help button home button Endocrine Society Endocrinology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology, doi:10.1210/en.2006-1577
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
148/8/4080    most recent
Author Manuscript (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Molinari, C.
Right arrow Articles by Vacca, G.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Molinari, C.
Right arrow Articles by Vacca, G.
Endocrinology Vol. 148, No. 8 4080-4090
Copyright © 2007 by The Endocrine Society

Prolactin Induces Regional Vasoconstriction through the ß2-Adrenergic and Nitric Oxide Mechanisms

Claudio Molinari, Elena Grossini, David A. S. G. Mary, Francesca Uberti, Ezio Ghigo, Flavio Ribichini, Nicola Surico and Giovanni Vacca

Laboratorio di Fisiologia, Dipartimento di Medicina Clinica e Sperimentale, Facoltà di Medicina e Chirurgia, Università del Piemonte Orientale "A. Avogadro," I-28100 Novara, Italy

Address all correspondence and requests for reprints to: Prof. C. Molinari, Facoltà di Medicina e Chirurgia, via Solaroli 17, I-28100 Novara, Italy. E-mail: molinari{at}med.unipmn.it.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 References
 
Prolactin has been associated with many effects and has been implicated in the pathogenesis of pregnancy-related hypertensive disorders, although little is known about its vascular effects. The present study was designed to determine the primary effect of prolactin on regional vascular beds and the mechanisms involved. In 37 anesthetized pigs, the infusion of 0.17 µg/kg·min of prolactin at constant heart rate and arterial pressure decreased coronary, mesenteric, renal, and iliac blood flow. This response was graded in further five pigs by increasing the infused dose of the hormone between 0.017 and 1 µg/kg·min. In 22 of the 37 pigs, blockade of cholinergic receptors (five pigs) and of {alpha}-adrenoceptors (five pigs) did not affect the prolactin-induced vascular response, which was abolished by blockade of ß2-adrenoceptors (five pigs) and by blockade of vascular nitric oxide (NO) synthase (seven pigs). In 15 of the 37 pigs the increases in measured blood flows caused by iv infusion of isoproterenol (five pigs) and by intraarterial administration of acetylcholine (five pigs) and of sodium nitroprusside (five pigs) were significantly reduced by infusion of prolactin. Moreover, the treatment of porcine aortic endothelial cells by prolactin caused a reduction of NO production and of the phosphorylation of ERK, Akt, and p38, which was prevented by the concomitant treatment by the ß2-adrenergic agonist albuterol. The present study showed that iv infusion of prolactin primarily caused coronary, mesenteric, renal, and iliac vasoconstriction. These effects were brought about by the inhibition of a vasodilatory ß2-adrenergic receptor-mediated effect related to the NO intracellular pathway.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 References
 
THE HORMONE PROLACTIN has been associated, in addition to its role in lactation and reproduction, with a multitude of effects throughout the body (1, 2). In particular, prolactin has been linked to the pathogenesis of pregnancy-related hypertensive disorders (3, 4, 5, 6). However, the levels of this hormone in such disorders have been reported to be either elevated, decreased, or within normal limits (7, 8, 9, 10, 11, 12, 13). Fundamentally, there has been insufficient evidence available on the primary effects of prolactin on blood flow and resistance in intact blood vessels despite findings linking it to vascular effects. For instance, iv infusion of prolactin has been found to increase arterial pressure in decerebrate rabbits (14), and to reduce renal blood flow, increase body fluid volume, and enhance the pressor response to norepinephrine in the rat (15, 16). The N-terminal 16-kDa fragment of prolactin has been shown to inhibit the relaxation of coronary vessels of isolated perfused animal hearts (17), and there have been reports of impairment of endothelial vasodilatory function and insulin sensitivity in patients with pituitary adenoma and hyperprolactinemia (18, 19).

Therefore, the present work was planned in two phases. In the first, the primary in vivo effects of the acute administration of prolactin on coronary, mesenteric, renal, and iliac blood flow and the mechanisms involved were investigated in controlled experiments in anesthetized pigs. This was achieved by iv infusing the hormone while preventing changes in heart rate and arterial blood pressure to avoid the secondary interference by reflex and local metabolic and physical effects. In addition, a dose-response study was also performed.

In the second phase, performed in porcine aortic endothelial cells (PAE), we examined the involvement of intracellular pathways related to nitric oxide (NO) mechanisms in the responses to prolactin.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 References
 
In vivo experiments
The experiments were carried out in 47 pigs, weighing 73–79 kg, supplied by an accredited dealer (Azienda Agricola Ticozzi, Trecate, Novara, Italy). The animals, which were fasted overnight, were anesthetized with intramuscular ketamine (20 mg/kg; Parke-Davis, Milan, Italy) followed after about 15 min by iv sodium pentobarbitone (15 mg/kg; Siegfried, Zofingen, Switzerland), after which they were artificially ventilated with oxygen-enriched air using a respiratory pump (Harvard 613; Harvard Apparatus, South Natick, MA). Anesthesia was maintained throughout the experiments by continuous iv infusion of sodium pentobarbitone (7 mg/kg·h) and assessed as previously reported (20) from responses of the animals to somatic stimuli. The experiments were carried out in accordance with national guidelines (D.L.G.S. 27/01/1992, no. 116).

Pressures in the ascending aorta and in the right atrium were recorded using pressure transducers (Statham P23 XL; Gould, Valley View, OH) and catheters inserted into the right femoral artery and the right external jugular vein, respectively. The chest was opened in the left fourth intercostal space, the pericardium was cut and an electromagnetic flowmeter probe (model BL 613; Biotronex Laboratory Inc., Chester, MD) was positioned around the proximal part of the anterior descending coronary artery. The abdomen was opened with a midline incision and a flowmeter probe was positioned near the origin of the superior mesenteric, left renal, and left external iliac arteries. Distal to the probe a plastic snare was placed around each artery for zero blood flow assessment. Each probe was calibrated in vitro at the end of each experiment.

Left ventricular pressure was measured via a catheter inserted through the left atrium and connected to a pressure transducer (Statham P23 XL; Gould). The frequency response of this system was flat (±5%) up to 40 Hz. To pace the heart, electrodes were sewn on the left atrial appendage and connected to a stimulator (model S8800; Grass Instruments, Quincy, MA) delivering pulses of 3–5 V with 2 ms duration at the required frequency. Arterial blood samples were used to measure pH, arterial partial pressures of oxygen and carbon dioxide (PO2 and PCO2) (with a gas analyzer; ABL 505; Radiometer, Copenhagen, Denmark), and the hematocrit. In the present study, the animals were artificially ventilated with oxygen-enriched air, and values of pH and PCO2 were maintained within normal limits during the experiments by the iv infusion of a solution of 2.8% sodium bicarbonate and by adjusting the respiratory stroke volume, when necessary (20).

To prevent changes in arterial blood pressure during the experiments, a cannula was introduced into the left internal mammary artery and connected to a reservoir containing Ringer solution (SIFRA-Societa’ Italiana Farmaceutici Ravizza, Verona, Italy) kept at 38 C. The reservoir was pressurized using compressed air, which was controlled with a Starling resistance, and pressure within the reservoir was measured by a mercury manometer. This method has been shown in anesthetized pigs to allow the arterial blood pressure to be maintained at steady levels without significant changes in filling pressures of the heart or the hematocrit (21, 22). Coagulation of the blood was avoided by the iv injection of heparin (Parke-Davis; initial doses of 500 IU/kg, and subsequent doses of 50 IU/kg every 30 min). The rectal temperature of the pigs was monitored and kept between 38–40 C using an electric pad.

Mean and phasic aortic blood pressure, mean right atrial pressure, left ventricular pressure, and mean and phasic coronary, mesenteric, renal, and iliac blood flow were monitored and recorded together with heart rate and the maximum rate of change of left ventricular systolic pressure (dP/dtmax) using an electrostatic strip-chart recorder (Gould ES 2000; Gould). The heart rate was obtained from the electrocardiogram with a ratemeter (ECG/Biotach amplifier, model 13–4615-65 A; Gould). The frequency response of the differentiator used to obtain left ventricular dP/dtmax was flat (±5%) up to 150 Hz.

To calculate coronary vascular resistance, the difference between mean aortic blood pressure and mean left ventricular pressure during diastole was considered as the coronary pressure gradient. Coronary vascular resistance was calculated as the ratio between this pressure gradient and mean diastolic coronary blood flow. The diastolic period of measurement was defined as starting when ventricular pressure reached its minimum value after systole and ended when it increased at the end of diastole. Mesenteric, renal, and iliac vascular resistance was calculated as the ratio between mean aortic blood pressure and mean mesenteric, renal, and iliac blood flow.

At the end of the experiment, each animal was killed by an iv injection of 90 mg/kg sodium pentobarbitone.

In vitro experiments
PAE cells were cultured in DMEM (DMEM Glutamax 1x; Invitrogen, Carlsbad, CA) supplemented with 10% fetal calf serum and 1% penicillin-streptomycin (Sigma, St. Louis, MO). Cultures were maintained at 37 C with 5% CO2. Before treatments, 1 x 104 cells were plated in 96-well plates with DMEM 0% fetal calf serum without phenol red for 6 h.

Experimental protocol: in vivo experiments
The experiments were begun after at least 30 min of steady-state conditions with respect to measured hemodynamic variables. In a total of 47 pigs, changes in heart rate and arterial blood pressure were avoided by pacing the heart to a frequency higher, by 20 beats per minute, than that observed during the steady state and by connecting the arterial system to the pressurized reservoir. After at least 10 min of steady-state conditions, the experiments were carried out by iv infusing either a solution of prolactin (from sheep pituitary, 99% purity; Sigma) obtained by dissolving the hormone in saline or the saline only, in a random order. The infusions, performed by means of a needle inserted distal to each probe, were completed in a period of 15 min by using an infusion pump (model 22; Harvard Apparatus) working at constant rate of 1 ml/min. In each pig, the dose of the hormone infused was of 0.17 µg/kg of body weight per minute. This corresponded to the dose of 10 µg/kg of body weight per hour that has been previously shown to increase arterial pressure in rabbits (14). After the infusion was stopped, observations were continued for 20 min.

Recordings taken for 10 min during the steady state before infusion of prolactin were used as control. Measurements of hemodynamic variables were obtained during the last 5 min of infusion in the steady state and compared with control values. The effects of infusion of prolactin on measured blood flows were studied in 37 pigs. In five pigs, a dose-response study was carried out by gradually increasing the infused dose of prolactin in 11 steps from a minimum value of 0.017 µg/kg·min to a maximum value of 1 µg/kg·min. Each dose was infused for 15 min and the resulting changes in blood flow were compared with control values obtained before starting the infusion.

The mechanisms of the response of measured blood flows to the infusion of prolactin were studied in the group of 37 pigs by repeating the experiment after hemodynamic variables had returned to control levels. In five pigs, prolactin was infused after blockade of cholinergic receptors with iv administration of atropine (0.5 mg/kg; Sigma); in five pigs, after blockade of {alpha}-adrenergic receptors with iv administration of phentolamine (1 mg/kg; Ciba Geigy, Varese, Italy); and in five pigs, after blockade of ß2-adrenergic receptors with iv administration of butoxamine (2.5 mg/kg; Sigma). In seven pigs, prolactin was infused after blockade of vascular NO synthase with intraarterial administration of N{omega}-nitro-L-arginine methyl ester (L-NAME; Sigma) at a dose of 2 mg/ml·min of measured blood flow. All the blocking agents were given in the absence of pacing of the heart and without controlling arterial blood pressure and their effects on hemodynamic variables were measured in the steady state. In all subsequent experiments, changes in heart rate and arterial blood pressure were prevented. In five of the seven pigs that received intraarterial L-NAME, prolactin was infused for 15 min first, after injecting the blocking agent into the coronary artery. The infusion of the hormone was then repeated after injecting L-NAME into the mesenteric artery, after injecting L-NAME into the renal artery, and, finally, after injecting L-NAME into the iliac artery. In the remaining two pigs, the infusion of the hormone was performed after injecting L-NAME into all four arteries. In these two pigs and in two of the butoxamine-treated pigs, the infusion of prolactin was performed when a steady state was attained during a continuous iv infusion of papaverine (Sigma) at a dose of 3.5–4.5 mg/kg·h. This procedure was used to reverse the increase in regional vascular resistance caused by the two blocking agents. In 10 pigs, the increases in coronary, mesenteric, renal, and iliac blood flow caused by intraarterial administration of acetylcholine (0.025 µg for each milliliter per minute of measured blood flow; five pigs) or by intraarterial administration of sodium nitroprusside (0.07 µg for each milliliter per minute of measured blood flow; five pigs) were assessed at constant heart rate and arterial blood pressure. After blood flows had returned to control levels, the effect of infusion of prolactin on the acetylcholine and sodium nitroprusside-induced blood flow increases was assessed by repeating the intraarterial administration of acetylcholine or sodium nitroprusside during the last 5 min of the hormone infusion. In the remaining five pigs of the group and in a further five pigs, the effect of 5 min iv infusion of isoproterenol (0.05 µg/kg·min) on baseline values of heart rate at constant arterial blood pressure was assessed. After hemodynamic variables had returned to control values (within 10 min), the isoproterenol infusion at constant arterial blood pressure was repeated while pacing the heart to a frequency higher, by 20 beats per minute, than that observed during the previous infusion of isoproterenol to assess the increases in coronary, mesenteric, renal, and iliac blood flow caused by the ß-adrenergic agent. After blood flows had returned to control levels, in the first five of these pigs the effect of infusion of prolactin on the isoproterenol-induced blood flow increases was assessed by repeating the infusion of the ß-adrenergic agent during the last 5 min of the hormone infusion. In the other five pigs, the infusion of isoproterenol was repeated after intraarterial administration of L-NAME (2 mg/ml·min of measured blood flow).

Experimental protocol: in vitro experiments
Measurement of NO production.
NO production in cultured supernatants from PAE cells was determined using the Griess method (Promega), following the manufacturer’s instruction. Cells were treated with the ß2-adrenergic agonist (10 µM albuterol; Sigma), butoxamine (100 µM), acetylcholine chlorohydrate (10 µM), and L-NAME (10 mM) in presence or absence of 680 ng/ml prolactin administered for 1 or 10 min. This concentration of prolactin has been shown in a preliminary dose-response study to induce the maximum effect in these cells. Every sample was also tested in presence of the phosphatidylinositol 3-kinase (PI3-K) inhibitor (100 nM wortmannin; Sigma), the p38 MAPK inhibitor (1 µM SB203580; Sigma), or the MAPK kinase (MEK) 1 inhibitor (10 µM UO126; Sigma). These inhibitors were tested in the basal medium without agents as well. At the end of all treatments, the supernatants of the samples were mixed with equal volume of Griess reagents, and, after 10 min, the absorbance at 570 nm was measured by a spectrometer (BS1000 Spectra Count). NO production was calculated by a standard curve generated with sodium nitrate standard in the same medium used for the samples and normalized by the protein content of corresponding wells.

Western blot analysis.
The PAE cells were incubated in phenol red-free medium without serum for 18 h and then treated with the same agents at the same concentration used for Griess method. They were then washed twice with ice-PBS 1x supplemented with 1:200 sodium orthovanadate and lysed in ice buffer (25 mM HEPES, 135 mM NaCl, 1% Nonidet P-40, 5 mM EDTA, 5 mM EGTA, 1 mM ZnCl2, 50 mM NaF, 10% glycerol) supplemented with 1:200 sodium orthovanadate (Sigma) and 1:100 protease-inhibitor cocktail (Sigma). The cells were solubilized with lysis buffer for 15 min at 4 C. The lysates were centrifuged at 12,000 x g for 15 min, and the extracts protein were quantified by bicinchoninic acid (BCA) protein assay (Pierce, Rockford, IL). Equal amounts of protein were dissolved in 5x Laemmly buffer, boiled and separated on SDS 8% polyacrylamide gels at 120 V (SDS-PAGE; Bio-Rad, Hercules, CA), and the proteins were transferred to polyvinylidene difluoride membranes (Amersham Pharmacia Biotech, Piscataway, NJ). Blocking was done in 100% methanol, and then the membranes were incubated overnight with various specific primary antibodies anti-phospho-ERK-(Thr202/Tyr204), anti-ERK1/2, anti-phospho-Akt-Ser473, anti-Akt, anti-phospho-p38(Thr180/Tyr182), anti-p38, and anti-ß-actin (Cell Signaling, Beverly, MA). Immunoreactive bands in the immunoblotting were visualized with horseradish peroxidase-coupled goat-antirabbit IgG (NEM Life Science Products, Brussels, Belgium) and goat antimouse IgG by using the chemiluminescence system, enhanced chemiluminescence (Perkin Elmer Life Science, Boston, MA). All levels of phosphorylation were quantified by densitometry and verified through ß-actin detection.

Statistical analysis
Student’s paired t test was used to examine changes in measured variables caused by prolactin infusion. ANOVA for repeated measurements was used to examine the effects of successive procedures on measured blood flows. A value of P < 0.05 was considered statistically significant. Group data are presented as means ± SD (range).


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
References
 
In vivo experiments
In all pigs, recordings commenced approximately 5 h after the induction of anesthesia. Values of pH, PO2, and PCO2 of arterial blood were, respectively, 7.40 ± 0.01 (7.38–7.43), 118 ± 9 (102–141), and 39.1 ± 1 (37–41) mm Hg and the hematocrit was 38.3 ± 1.1% (36–41%).

Effects of infusion of prolactin.
In the group of 37 pigs, infusion of the vehicle did not cause changes in the control values of measured hemodynamic variables. Group values of data and changes in mean coronary, mesenteric, renal, and iliac blood flow caused by infusion of prolactin are shown in Table 1Go and Fig. 1Go, respectively. In each pig, infusion of prolactin caused a statistically significant decrease (P < 0.01) in mean coronary, mesenteric, renal, and iliac blood flow. Group decreases in these flows, respectively, amounted to –20 ± 2.6% (13.7–24.3%), –12.9 ± 2.2% (8.4–17.4%), –11.3 ± 1.9% (6.9–15.2%), and –13.9 ± 2.4% (9–18.4%) of the control values and corresponded to increases in coronary, mesenteric, renal, and iliac vascular resistance of 21.2 ± 3.3% (14.7–27.6%), 15.2 ± 3.2% (8.3–21.3%), 13.6 ± 3.3% (5.3–20%), and 16.4 ± 3.5% (11.1–23.4%) from control values of 1.09 ± 0.15 (0.88–1.40), 0.092 ± 0.014 (0.074–1.127), 0.21 ± 0.03 (0.17–0.26), and 0.93 ± 0.12 (0.72–1.24) mm Hg/ml·min. Changes in left ventricular dP/dtmax, mean right atrial pressure, and left ventricular end-diastolic pressure during these experiments were not significant (Table 1Go). An example of the above response is shown in Fig. 2Go. In the 37 pigs examined, the effect of prolactin began within about 3 min after starting the infusion and reached a steady state in about 5 min. Measured blood flows returned to control values within 10 min after the end of the infusion. These results indicate that infusion of prolactin causes coronary, mesenteric, renal, and iliac vasoconstriction.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Changes in hemodynamic variables caused by iv infusion of 0.17 µg/kg of body weight per minute of prolactin in 37 pigs

 

Figure 1
View larger version (12K):
[in this window]
[in a new window]

  		FIG. 1. The response of mean coronary blood flow (CBF), mean mesenteric blood flow (MBF), mean renal blood flow (RBF), and mean iliac blood flow (IBF) to the iv infusion of prolactin in 37 pigs. a, P < 0.01 vs. control.

 

Figure 2
View larger version (15K):
[in this window]
[in a new window]

  		FIG. 2. Example of experimental recordings showing the hemodynamic effects of the iv infusion of prolactin in one pig. From top to bottom: heart rate (HR), mean and phasic aortic blood pressure (ABP), left ventricular pressure (LVP), maximum rate of change of left ventricular pressure (dP/dtmax), mean right atrial pressure (RAP), mean and phasic coronary blood flow (CBF), mean and phasic mesenteric blood flow (MBF), mean and phasic renal blood flow (RBF), mean and phasic iliac blood flow (IBF). The arrow indicates the beginning of the infusion.

 
Dose-response study.
In the five pigs, control values of mean coronary, mesenteric, renal, and iliac blood flow were, respectively, 61.5 ± 6.5 (53.2–70.5), 1033 ± 55 (985–1121), 472 ± 31 (433–507), and 105 ± 10 (96–119) ml/min. The results obtained by gradually increasing the infused dose of prolactin are shown in Fig. 3Go. The threshold dose of the hormone was found to be between 0.07–0.10 µg/kg·min. Maximal effects for all measured blood flows were observed at a dose of 0.67 µg/kg·min.


Figure 3
View larger version (15K):
[in this window]
[in a new window]

  		FIG. 3. Response of coronary blood flow (CBF), mesenteric blood flow (MBF), renal blood flow (RBF), and iliac blood flow (IBF) to graded increases in the infused dose of prolactin between 0.017 and 1 µg/kg·min in five pigs. The means of percentage changes in blood flow obtained during the test period of measurement are plotted against the logarithm of the doses. C, Control value before infusions. The bars indicate SD.

 
Experiments after blockade of cholinergic receptor, {alpha} and ß2 adrenergic receptors, and vascular NO synthase.
The effects of the administration of the blocking agents on control values of heart rate, mean aortic blood pressure, left ventricular dP/dtmax, and mean coronary, mesenteric, renal, and iliac blood flow are shown in Table 2Go. In two of the butoxamine-treated pigs and in two of the L-NAME-treated pigs, infusion of papaverine decreased coronary vascular resistance by 0.27 ± 0.08 (0.21–0.37; P < 0.01) mm Hg/ml·min, decreased mesenteric vascular resistance by 0.026 ± 0.013 (0.013–0.037; P < 0.05) mm Hg/ml·min, decreased renal vascular resistance by 0.07 ± 0.01 (0.05–0.08; P < 0.01) mm Hg/ml·min, and decreased iliac vascular resistance by 0.25 ± 0.12 (0.15–0.35; P < 0.05) mm Hg/ml·min. In the same four pigs, the increases in coronary, mesenteric, renal, and iliac vascular resistance caused by butoxamine and L-NAME alone were, respectively, 0.26 ± 0.08 (0.18–0.33; P < 0.01), 0.025 ± 0.014 (0.012–0.038; P < 0.05), 0.06 ± 0.02 (0.03–0.08; P < 0.01), and 0.21 ± 0.12 (0.10–0.32; P < 0.05) mm Hg/ml·min.


View this table:
[in this window]
[in a new window]

  		TABLE 2. The effects of blockade of cholinergic receptors, adrenergic receptors, and vascular nitric oxide synthase on hemodynamic variables in 22 pigs

 
Blockade of cholinergic and {alpha}-adrenergic receptors did not affect the prolactin-induced decrease in coronary, mesenteric, renal, and iliac blood flow, an effect that was completely abolished by blockade of ß2 adrenergic receptors and vascular NO synthase.

Mean changes in blood flows obtained after blockade of cholinergic and {alpha}-adrenergic receptors are shown in Fig. 4Go, A and B. ANOVA for repeated measurements showed that the decreases in measured blood flows caused by prolactin before and after blockade of cholinergic and {alpha}-adrenergic receptors were not significant (at least F = 0.43, P > 0.50).


Figure 4
View larger version (9K):
[in this window]
[in a new window]

  		FIG. 4. The effect of blockade of cholinergic (A), {alpha}-adrenergic (B) and ß2-adrenergic (C) receptors, and NO synthase (D) on responses of coronary blood flow (CBF), mesenteric blood flow (MBF), renal blood flow (RBF), and iliac blood flow (IBF) to the iv infusion of prolactin. a, P < 0.01 vs. control.

 
Mean changes in blood flows obtained after blockade of ß2-adrenergic receptors are shown in Fig. 4CGo. ANOVA for repeated measurements showed a significant difference in the response of coronary, mesenteric, renal, and iliac blood flow before and after blockade of ß2-adrenergic receptors (at least F = 44.03, P < 0.01).

Mean changes in blood flows obtained after injection of L-NAME are shown in Fig. 4DGo. ANOVA for repeated measurements showed a significant difference in the response of coronary, mesenteric, renal, and iliac blood flow before and after blockade of vascular NO synthase (at least F = 81.64, P < 0.01).

In the two pigs in which L-NAME was injected in all four arteries, infusion of prolactin did not cause changes in measured blood flows (P > 0.05).

These results indicate that the mechanisms of the coronary, mesenteric, renal, and iliac vasoconstriction caused by infusion of prolactin were mediated by ß2-adrenergic receptors and involved the release of NO.

Experiments with acetylcholine and sodium nitroprusside.
In the five pigs treated, intraarterial administration of acetylcholine caused significant increases in coronary, mesenteric, renal, and iliac blood flow. Mean changes are shown in Fig. 5Go (open columns). When the intraarterial administration of acetylcholine was performed during the last 5 min of prolactin infusion the responses of these flows to acetylcholine were reduced by 35.7 ± 6.9% (27.4–45.8%), 37.1 ± 8.1% (27.9–48.5%), 30.2 ± 6.9% (20.5–39.4%), and 35.3 ± 11.4% (20.8–50%), respectively. Mean changes are shown in Fig. 5Go (filled columns). ANOVA for repeated measurements showed a significant difference in the increases in measured blood flows caused by acetylcholine before and during infusion of prolactin (at least F = 42.94, P < 0.05).


Figure 5
View larger version (12K):
[in this window]
[in a new window]

  		FIG. 5. The effect of acetylcholine on coronary blood flow (CBF), mesenteric blood flow (MBF), renal blood flow (RBF), and iliac blood flow (IBF) in the absence (open columns) or presence (filled columns) of prolactin. a, P < 0.01 vs. control; b, P < 0.01 vs. a.

 
In the five pigs treated, intraarterial administration of sodium nitroprusside caused significant increases in coronary, mesenteric, renal, and iliac blood flow. Mean changes are shown in Fig. 6Go (open columns). When the intraarterial administration of sodium nitroprusside was performed during the last 5 min of prolactin infusion the responses of these flows to sodium nitroprusside were reduced by 36 ± 3.5% (30–39.1%), 34.1 ± 6.9% (30–45.6%), 30.7 ± 1.7% (28.9–33%), and 36.4 ± 6.7% (25–42.1%), respectively. Mean changes are shown in Fig. 6Go (filled columns). ANOVA for repeated measurements showed a significant difference in the increases in measured blood flows caused by sodium nitroprusside before and during infusion of prolactin (at least F = 63.16, P < 0.01).


Figure 6
View larger version (12K):
[in this window]
[in a new window]

  		FIG. 6. The effect of sodium nitoprusside on coronary blood flow (CBF), mesenteric blood flow (MBF), renal blood flow (RBF), and iliac blood flow (IBF) in the absence (open columns) or presence (filled columns) of prolactin. a, P < 0.01 vs. control; b, P < 0.01 vs. a.

 
These results confirmed that the NO plays a role in the coronary, mesenteric, renal, and iliac vasoconstriction caused by infusion of prolactin.

Experiments with isoproterenol.
In the 10 pigs treated, a preliminary infusion of isoproterenol at constant arterial blood pressure caused an increase in heart rate of 33.4 ± 3.3 (29–39; P < 0.01) beats per minute from control values of 91.2 ± 5.7 (85–102) beats per minute.

In five of these pigs, infusion of the ß-adrenergic agent at constant heart rate and arterial blood pressure caused significant increases in coronary, mesenteric, renal, and iliac blood flow. Mean changes are shown in Fig. 7AGo (open columns). When isoproterenol was administered during the last 5 min of prolactin infusion, the responses of these flows to isoproterenol were reduced by 48.7 ± 12.2% (30.6–60.2%), 46.1 ± 7.2% (35.6–54.5%), 46.1 ± 5.9% (38.5–54.1%), and 47.9 ± 7.5% (39.1–57.1%), respectively. Mean changes are shown in Fig. 7AGo (filled columns). ANOVA for repeated measurements showed a significant difference in the increases in measured blood flows caused by isoproterenol before and during infusion of prolactin (at least F = 26.89, P < 0.05).


Figure 7
View larger version (10K):
[in this window]
[in a new window]

  		FIG. 7. The effect of isoproterenol on coronary blood flow (CBF), mesenteric blood flow (MBF), renal blood flow (RBF), and iliac blood flow (IBF) in the absence (open columns) or presence (filled columns) of prolactin (A) or L-NAME (B). a and c, P < 0.01 vs. control; b and d, P < 0.01 vs. a and c.

 
In the remaining five pigs, infusion of the ß-adrenergic agent at constant heart rate and arterial blood pressure caused significant increases in coronary, mesenteric, renal, and iliac blood flow. Mean changes are shown in Fig. 7BGo (open columns). Subsequent infusion of L-NAME caused a reduction of the responses of these flows to isoproterenol of 28 ± 2.1% (25.9–30.8%), 26.7 ± 1.9% (25.7–30.5%), 28.1 ± 3.3% (23.6–32.7%), and 33.6 ± 8.7% (25–44.8%), respectively. Mean changes are shown in Fig. 7BGo (filled columns).

ANOVA for repeated measurements showed a significant difference in the increases in measured blood flows caused by isoproterenol before and after intraarterial administration of L-NAME (at least F = 37.81, P < 0.05).

These results confirmed that the coronary, mesenteric, renal, and iliac vasoconstriction caused by infusion of prolactin were mediated by ß2-adrenergic receptors.

In vitro experiments
NO production in the absence of MAPKs, PI3-K, p38 inhibitors.
As depicted in Fig. 8AGo, the application of prolactin (680 ng/ml) induced a reduction of NO production (P < 0.05). At 1 min after the beginning of the administration this effect amounted to 12% and was over at 10 min.


Figure 8
View larger version (13K):
[in this window]
[in a new window]

  		FIG. 8. NO production measurement in PAE cells. A, Effect of various agents (PRL1, 1 min stimulation; PRL10, 10 min stimulation; LNAME&PRL, costimulation; BUTOX, 100 µM butoxamine; BUTOX&PRL, costimulation; ACH, 10 µM acetylcholine; ACH&PRL, costimulation; ALB, 10 µM albuterol; ALB&PRL, costimulation) in the absence of MAPKs, PI3-K, or p38 inhibitors. B, Effect of prolactin in the absence or presence of MAPKs, PI3-K, or p38 inhibitors (I, 10 µM UO126, 100 nM wortmannin, 1 µM SB203580). C, Effect of albuterol in the absence or presence of MAPKs, PI3-K, p38 inhibitors (I). D, Effect of the concomitant administration of prolactin and albuterol in the absence or presence of MAPKs, PI3-K, p38 inhibitors (I). a, P < 0.05 vs. control (C); b, P < 0.05; c, P < 0.05 vs. inhibitors (I).

 
Prolactin given together with L-NAME (10 mM) induced an insignificant reduction of NO after 1 min (Fig. 8AGo) and then failed to cause any other change in NO synthesis. After butoxamine (100 µM), the NO synthesis was acutely reduced by about 7%. The administration of butoxamine after PRL did not induce significant changes in NO levels (Fig. 8AGo).

When PAE cells were treated with albuterol (10 µM), a rapid increase of NO production by about 14% was observed. This increase was similar to that obtained with acetylcholine (10 µM; Fig. 8AGo). In the presence of prolactin, the effect of acetylcholine was abolished, whereas the effect of albuterol was reduced by about 50% (Fig. 8AGo).

Analysis of the intracellular pathway involved in NO production.
To clarify whether prolactin administration could have blocked the intracellular pathway to NO production, involving the PI3-K, the p38 MAPK, or MEK and considering that rapid NO production, also through ß-adrenoceptors, can be mediated via activation of the above intracellular pathways (23, 24, 25), we checked the role of these cascades for prolactin-ß2 adrenergic-dependent NO synthesis.

After the administration of wortmannin (PI3-K inhibitor; 100 nM), SB203580 (p38 MAPK inhibitor; 1 µM), or UO126 (MEK inhibitor; 10 µM), both prolactin and albuterol administration given alone did not change the basal NO production (Fig. 8Go, B and C); whereas, when the two substances were given together, a significantly lower NO production than the one caused by albuterol alone was observed (Fig. 8DGo).

Prolactin administration induced an inhibition of the phosphorylation of ERK1/2 by 40% and of Akt by 21%, as shown by MEK1 analysis, which is reported to have a wide range of IC50 values for the suppression of ERK1/2 activation (24), and of p38 by 24% (Fig. 9Go, A–C). Albuterol induced a significant increase of Akt phosphorylation by 120%, confirming data previously described (26). Interestingly, the ß2 agonist administration induced a phosphorylation of ERK1/2 by 55% and of p38 by 112% as well. The concomitant administration of prolactin and albuterol caused a significant reduction of phosphorylation caused by albuterol given alone (Fig. 9Go, A–C).


Figure 9
View larger version (33K):
[in this window]
[in a new window]

  		FIG. 9. Level of phosphorylation of ERK1/2 (A), Akt (B), and p38 (C) induced by prolactin and albuterol given alone or together. Abbreviations are the same as in Fig. 8Go. a, P < 0.05 vs. control; b, P < 0.05 vs. a; c, P < 0.05 vs. b.

 
Discussion
The present investigation has shown for the first time that iv infusion of prolactin primarily caused decreases in blood flow and increases in vascular resistance in the coronary, mesenteric, renal, and iliac vascular beds. The mechanisms of these effects were shown to involve ß2-adrenergic receptor-mediated effects related to the intracellular NO pathway.

In vivo experiments
The observed blood flow decreases in response to the iv infusion of prolactin can be attributed to a primary effect of the hormone and not to concomitant changes in hemodynamic variables. The heart rate and arterial blood pressure were kept constant and there were not significant changes in the filling pressures of the heart and left ventricular dP/dtmax. This excluded any secondary interference from reflex, local metabolic, and physical effects on the response of measured blood flows to infusion of prolactin. In addition, iv infusion of the vehicle alone at the same rate as that of prolactin did not reproduce any of the effects of infused hormone. Furthermore, the direct relationship between the hormone and its coronary, mesenteric, renal, and iliac responses was confirmed during the dose-response study, which showed that the decreases in regional blood flow could be augmented by increasing the dose of the infused hormone. Therefore, the present investigation showed that iv infusion of prolactin primarily caused coronary, mesenteric, renal, and iliac vasoconstriction, because this response did not involve changes in other hemodynamic variables.

Using such a controlled anesthetized animal preparation, mechanisms were examined by repeating the experiment after blocking cholinergic and adrenergic receptors. We used atropine and phentolamine to block cholinergic and {alpha}-adrenergic receptors. The dose of atropine used in this study has been previously used in anesthetized pigs to block cholinergic receptors (21, 27). The dose of 1 mg/kg phentolamine has been shown in the same experimental model to abolish the reflex coronary vasoconstriction caused by distension of the gallbladder (28), and the reflex splenic, mesenteric, renal, and iliac vasoconstriction caused by distension of the stomach (29). Similar doses of the blocking agents have been used in anesthetized pigs by other authors (30). Neither atropine nor phentolamine affected the responses to prolactin, indicating that the coronary, mesenteric, renal, and iliac vasoconstriction caused by the hormone did not involve cholinergic or {alpha}-adrenergic receptors. We used 2.5 mg/kg butoxamine to block ß2-adrenergic receptors, because this dose has been shown previously to abolish the increase in arterial blood pressure and the coronary vasoconstriction caused by growth hormone (31), and the mesenteric, renal, and iliac vasoconstriction caused by dehydroepiandrosterone (22). Infusion of prolactin after the administration of butoxamine did not cause any changes in measured blood flows, indicating that the coronary, mesenteric, renal, and iliac vasoconstriction elicited by the hormone involved ß2-adrenergic sympathetic effects. Although the blocking agent increased regional vascular resistance, this effect was not involved in the blockade of the response to prolactin, because infusion of the hormone did not elicit significant changes in coronary, mesenteric, renal, and iliac blood flow also when the increase in vascular resistance was reversed by papaverine. In addition, the infusion of prolactin reduced by about 45–50% the coronary, mesenteric, renal, and iliac vasodilation caused by infusion of 0.05 µg/kg·min of isoproterenol, a dose that has been previously used to examine postnatal changes in left ventricular systolic function and ventricular-vascular coupling in piglets (32) and to confirm in the same experimental model of the present work the mechanisms involved in the mesenteric, renal, and iliac vasoconstriction caused by dehydroepiandrosterone (22).

The findings that butoxamine induced vasoconstriction and abolished the response to prolactin and that prolactin significantly reduced the regional vasodilation caused by a ß-adrenergic agent suggest that the hormone caused coronary, mesenteric, renal, and iliac vasoconstriction by blocking a tonic vasodilatory effect mediated by ß2-adrenergic receptors. This finding is consistent with previous reports showing a tonic ß2-adrenergic receptor-mediated vasodilation in the coronary, mesenteric, renal, and iliac vascular beds of anesthetized pigs (22, 29, 31). Interestingly, the inhibition of isoproterenol-induced increase of blood flows caused by prolactin was higher than the one caused by L-NAME, which reduced the vasodilation by about 26–33% only. The higher effect of prolactin in comparison with L-NAME could be explained by the involvement of a wider ß-adrenergic intracellular pathway leading to NO synthesis.

The present findings also showed that the coronary, mesenteric, renal, and iliac vasoconstriction caused by infusion of prolactin involved both the endothelial release of NO and its intracellular pathway. Although the actual release of NO was not measured, the regional vasoconstriction elicited by infusion of the hormone was abolished by the local intraarterial administration of L-NAME, which is known to inhibit the formation of NO (33). The dose of 2 mg for 1 ml/min of measured blood flow of the blocking agent used is similar to that previously shown in anesthetized pigs to abolish the coronary, mesenteric, renal, and iliac vasodilation caused by iv infusion of 17ß-estradiol or progesterone (21, 34, 35) and by intraarterial infusion of testosterone (36) and the coronary, mesenteric, renal, and iliac vasoconstriction caused by iv infusion of dehydroepiandrosterone (22, 27). In the present study, the blocking effect of L-NAME was local to the vascular bed examined, because it did not affect the response of the other vascular beds to the infusion of prolactin. Also L-NAME increased regional vascular resistance. However, this effect did not influence our results, because infusion of prolactin did not elicit significant changes in measured blood flows even when the increases in regional vascular resistance were reversed by papaverine. In addition, the infusion of prolactin reduced by about 30–37% the coronary, mesenteric, renal, and iliac vasodilation caused by intraarterial administration of 0.025 µg for each milliliter per minute of measured blood flow of acetylcholine, a dose similar to that previously used in pigs to assess the inhibition of the release of NO caused by intracoronary injection of L-NAME (21). Interestingly, the infusion of prolactin after sodium nitroprusside reduced by about 34% the vasodilation caused by the NO donor, thus suggesting the involvement of intracellular NO pathway.

The present results, showing that the tonic ß2-adrenergic receptors-mediated vasodilatory effect blocked by infusion of prolactin involved the endothelial release of NO, are consistent with previously reported findings showing that the N-terminal 16-kDa fragment of prolactin inhibits acetylcholine-induced NO synthase activity in bovine umbilical vein endothelial cells and relaxation of coronary vessels of isolated perfused rat heart (17) and that the release of NO from the endothelium can modulate or mediate ß-adrenergic effects in the coronary and peripheral vasculature (37, 38, 39, 40, 41).

Similar effects have been found in the same animal model after the administration of growth hormone and human placental lactogen (31, 42, 43, 44), which are structurally related with prolactin.

In vitro experiments
The results found in PAE cells confirm the ones obtained in the anesthetized pigs. In the PAE cells, the administration of prolactin, at a dosage corresponding to the one that was able to induce the highest decrease of NO production, acutely reduced the NO production and the level of phosphorylation of ERK, p38, and Akt, which are known to be involved in the intracellular signaling of NO production, also through ß-adrenoceptors (23, 24, 25). The effect on NO synthesis was prevented by the concomitant administration of L-NAME, butoxamine, and of wortmannin, UO126, and SB203580. Thus, even if the measurement of the endothelial NO synthase activity was not performed, the results obtained support the hypothesis of the inhibition of endothelial NO synthesis at basis of the vasoconstriction caused by prolactin in the anesthetized pig. These results are in agreement with previous studies performed in endothelial cells showing the inhibition of the endothelial NO synthase by the active fragment of prolactin (17) involving the p38MAPK pathway (25).

In addition, the results obtained with albuterol confirmed the inhibition of a tonic vasodilatory ß2-adrenergic-receptor-mediated effect related to the release of NO as mechanism of action of the vasoconstriction induced by prolactin in the animal model. As previously described (23), the administration of albuterol induced an increase of NO production and of the phosphorylation of Akt, ERK1/2, and p38. Although the reported data demonstrate a relationship between ERK1/2 and ß2-adrenoceptors (45), the involvement of these proteins and of the p38 pathway in the NO production caused by the ß2-adrenergic stimulation is a new finding. The concomitant administration of prolactin and albuterol induced an increase of NO production significantly lower than the one observed with albuterol given alone. The analysis of level of phosphorylation of ERK1/2, Akt, and p38 confirms the supposed mechanism of a common intracellular pathway of action of prolactin and ß2-adrenergic receptor to NO production. Further studies will be necessary to verify if prolactin interferes directly with the ß2-adrenergic receptor.

The present findings, showing an effect of widespread vasoconstriction caused by prolactin, can be argued to add information about the physiological control of regional blood flow during pregnancy. Previous reports in anesthetized pigs have shown that 17ß-estradiol and progesterone cause vasodilation through mechanisms that involve the endothelial release of NO (21, 34, 35). The increase in maternal serum levels of prolactin that accompanies the increases in maternal serum levels of 17ß-estradiol and progesterone during pregnancy could represent a mechanism that can balance the vascular effects of these steroid hormones.

Our findings have important implications regarding the vasoactive effects of prolactin and pathogenesis of pregnancy-related hypertensive disorders. The precise mechanisms involved in such disorders have not been unequivocally determined; of the proposed genetic, humoral, and metabolic factors no single cause has been established (46, 47). The mechanisms of prolactin-induced vasoconstriction, namely alterations in the function of adrenergic receptors and endothelium, could at least be involved locally in the placenta as a factor initiating the development of hypertension during pregnancy. For instance, an imbalance between vasodilator and vasoconstrictor substances involving endothelial function is known to occur in such disorders (46). Also, endothelial dysfunction and changes in the function of adrenergic receptors have been related to the hypertensive disorders (47, 48, 49). Finally, chronic increase in prolactin levels has been associated with impairment of endothelial vasodilatory function (18, 19). Thus, our findings are consistent with mechanisms linking hormonal factors to endothelial function that could be relevant to pregnancy-related hypertensive disorders.

In conclusion, the present study has shown that iv infusion of prolactin causes coronary, mesenteric, renal, and iliac vasoconstriction. The mechanisms of this vascular response were shown to involve the inhibition of a tonic vasodilatory ß2-adrenergic-receptor-mediated effect related to the NO intracellular pathway.


   Acknowledgments
 
We thank the Azienda Ospedaliera Maggiore della Carità di Novara for its help.


   Footnotes
 
This paper was supported by grants of the Università del Piemonte Orientale "A. Avogadro".

Disclosure Statement: The authors have nothing to disclose.

First Published Online April 26, 2007

Abbreviations: MEK, MAPK kinase; NO, nitric oxide; PAE, porcine aortic endothelial; PI3-K, phosphatidylinositol 3-kinase.

Received November 27, 2006.

Accepted for publication April 17, 2007.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 References
 

  1. Bole-Feysot C, Goffin V, Edery M, Binart N, Kelly PA 1998 Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice. Endocr Rev 19:225–268[Abstract/Free Full Text]
  2. Goffin V, Binart N, Touraine P, Kelly PA 2002 Prolactin: the new biology of an old hormone. Ann Rev Physiol 64:47–67[CrossRef][Medline]
  3. Horrobin DF 1975 The possible role of prolactin in preeclampsia. Med Hypotheses 1:159–164[CrossRef][Medline]
  4. Redman CW, Bonnar J, Beilin LJ, McNeilly AS 1975 Prolactin in hypertensive pregnancy. Br Med J 8:304–306
  5. Oney T, Bellmann O, Kaulhausen H 1988 Relationship between serum prolactin concentration, vascular angiotensin sensitivity and arterial blood pressure during third trimester pregnancy. Arch Gynecol Obstet 243:83–90[CrossRef][Medline]
  6. Parra A, Ramirez-Peredo J 2002 The possible role of prolactin in preeclampsia: 2001, a hypothesis revisited a quarter of century later. Med Hypotheses 59:378–384[CrossRef][Medline]
  7. Yuen BH, Cannon W, Wooley S, Charles E 1978 Maternal plasma and amniotic fluid prolactin levels in normal and hypertensive pregnancy. Br J Obstet Gynaecol 85:293–298[Medline]
  8. Ranta T, Stenman UH, Unnerus HA, Rossi J, Seppala M 1980 Maternal plasma prolactin levels in preeclampsia. Obstet Gynecol 55:428–430[Abstract/Free Full Text]
  9. Jenkins DM, Soltan MH 1980 Plasma prolactin and puerperal blood pressure. Br J Obstet Gynaecol 87:597–599[Medline]
  10. Luciano AA, Varner MW 1984 Decidual, amniotic fluid, maternal and fetal prolactin in normal and abnormal pregnancies. Obstet Gynecol 63:384–388[Abstract/Free Full Text]
  11. Golander A, Kopel R, Lazebnik N, Frenkel Y, Spirer Z 1985 Decreased prolactin secretion by decidual tissue of preeclampsia in vitro. Acta Endocrinol (Copenhagen) 108:111–113[Medline]
  12. McCoshen JA, Tyson JE 1985 Altered prolactin bioactivity in amniotic fluid of hypertensive pregnancy. Obstet Gynecol 65:24–30[Abstract/Free Full Text]
  13. Miyakawa I, Taniyama K, Sakata M, Yamaguchi M, Mori N 1986 Prolactin in severe toxaemia and pregnancy. Eur J Obstet Gynecol Reprod Biol 23:25–30[CrossRef][Medline]
  14. Horrobin DF, Manku MS, Burstyn PG 1973 Effect of intravenous prolactin infusion on arterial blood pressure in rabbits. Cardiovasc Res 7:585–587[Medline]
  15. Bliss DJ, Lote CJ 1982 Effect of prolactin on urinary excretion and renal hemodynamics in conscious rats. J Physiol 322:399–407[Medline]
  16. Mills DE, Ward RP 1986 Effect of prolactin on blood pressure and cardiovascular responsiveness in the rat. Proc Soc Exp Biol Med 181:3–8[Abstract]
  17. Gonzalez C, Corbacho AM, Eiserich JP, Garcia C, Lopez-Barrera F, Morales-Tlalpan V, Espinosa AB, Diaz-Munoz M, Rubio R, Lin S-H, Martinez de la Escalera G, Clapp C 2004 16K-Prolactin inhibits activation of endothelial nitric oxide synthase, intracellular calcium mobilization, and endothelium-dependent vasorelaxation. Endocrinology 145:5714–5722[Abstract/Free Full Text]
  18. Foss MC, Paula FJ, Paccola GM, Piccinato CE 1995 Peripheral glucose metabolism in human hyperprolactinemia. Clin Endocrinol 43:721–726[Medline]
  19. Yavuz D, Deyneli O, Akpinar I, Yildiz E, Gozu H, Sezgin O, Haklar G, Akalin S 2003 Endothelial function, insulin sensitivity and inflammatory markers in hyperprolactinemic pre-menopausal women. Eur J Endocrinol 149:187–193[Abstract]
  20. Linden RJ, Mary DASG 1983 The preparation and maintenance of anaesthetized animals for the study of cardiovascular function. In: Linden RJ, ed. Life sciences. Techniques in cardiovascular physiology. Vol P3/1. Shannon, Ireland: Elsevier Science Publishers; 1–22
  21. Vacca G, Battaglia A, Grossini E, Mary DASG, Molinari C, Surico N 1999 The effect of 17ß-oestradiol on regional blood flow in anaesthetized pigs. J Physiol 514:875–884[Abstract/Free Full Text]
  22. Molinari C, Battaglia A, Grossini E, Mary DASG, Vassanelli C, Vacca G 2004 The effect of dehydroepiandrosterone on regional blood flow in prepubertal anaesthetized pigs. J Physiol 557:307–319[Abstract/Free Full Text]
  23. Queen LR, Ji Y, Xu B, Youmg L, Yao K, Wyatt AW, Rowlands DJ, Siow RCM, Mann GE, Ferro A 2006 Mechanisms underlying ß2-adrenoceptor-mediated nitric oxide generation by human umbilical vein endothelial cells. J Physiol 576:585–594[Abstract/Free Full Text]
  24. Isenovic E, Walsh MF, Muniyappa R, Bard M, Diglio CA, Sowers JR 2002 Phosphatidylinositol 3-kinase may mediate isoproterenol-induced vascular relaxation in part through nitric oxide production. Metabolism 51:380–386[CrossRef][Medline]
  25. Lee SH, Nishino M, Mazumdar T, Garcia GE, Galfione M, Lee FL, Lee CL, Liang A, Kim J, Feng L, Eissa NT, Lin SH, Yu-Lee LY 2005 16-kDa Prolactin down-regulates inducible nitric oxide synthase expression through inhibition of the signal transducer and activator of transcription 1/IFN regulatory factor-1 pathway. Cancer Res 65:7984–7992[Abstract/Free Full Text]
  26. Liu JC, Baker RE, Sun C, Sundmark VC, Elsholz H 2002 Activation of GO-coupled dopamine D2 receptor inhibits ERK1/ERK2 in pituitary cells. J Biol Chem 277:35819–35825[Abstract/Free Full Text]
  27. Molinari C, Battaglia A, Grossini E, Mary DASG, Vassanelli C, Vacca G 2003 The effect of dehydroepiandrosterone on coronary blood flow in prepubertal anaesthetized pigs. J Physiol 549:937–944[CrossRef]
  28. Vacca G, Battaglia A, Grossini E, Mary DASG, Molinari C 1996 Reflex coronary vasoconstriction caused by gallbladder distension in anesthetized pigs. Circulation 94:2201–2209[Abstract/Free Full Text]
  29. Vacca G, Mary DASG, Battaglia A, Grossini E, Molinari C 1996 The effect of distension of the stomach on peripheral blood flow in anaesthetized pigs. Exp Physiol 81:385–396[Abstract]
  30. Gregory NG, Wotton SB 1981 Autonomic and non-autonomic control of cardiovascular function in stress-sensitive pigs. J Vet Pharmacol Ther 4:183–191[Medline]
  31. Vacca G, Battaglia A, Chiorboli E, Grossini E, Mary DASG, Molinari C 1998 Haemodynamic effects of the intravenous administration of growth hormone in anaesthetized pigs. Pflugers Arch 436:159–167[CrossRef][Medline]
  32. Cassidy SC, Chan DP, Allen HD 1997 Left ventricular systolic function, and ventricular-vascular coupling: a development study in piglets. Pediatr Res 42:273–281[Medline]
  33. Henderson AH 1991 Endothelium in control. Br Heart J 65:116–125[Free Full Text]
  34. Molinari C, Battaglia A, Grossini E, Mary DASG, Stoker JB, Surico N, Vacca G 2001 The effect of progesterone on coronary blood flow in anaesthetized pigs. Exp Physiol 86:101–108[Abstract]
  35. Molinari C, Battaglia A, Grossini E, Mary DASG, Surico N, Vacca G 2001 Effect of progesterone on peripheral blood flow in prepubertal female anaesthetized pigs. J Vasc Res 38:569–577[CrossRef][Medline]
  36. Molinari C, Battaglia A, Grossini E, Mary DASG, Vassanelli C, Vacca G 2002 The effect of testosterone on regional blood flow in prepubertal anaesthetized pigs. J Physiol 543:65–372
  37. Rubanyi G, Vanhoutte PM 1985 Endothelium-removal decreases relaxations of canine coronary arteries caused by ß-adrenergic agonists and adenosine. J Cardiovasc Pharmacol 7:139–144[Medline]
  38. Young MA, Vatner SF 1986 Enhanced adrenergic constriction of the iliac artery with removal of endothelium in conscious dogs. Am J Physiol 250:H892–H897
  39. Quillen J, Selke F, Banitt P, Harrison D 1992 The effect of norepinephrine on the coronary microcirculation. J Vasc Res 29:2–7[Medline]
  40. Parent R, al-Obaidi M, Lavallée M 1993 NO formation contributes to ß-adrenergic dilation of resistance coronary vessels in conscious dogs. Circ Res 73:241–251[Abstract/Free Full Text]
  41. Di Carlo SE, Patil RD, Collins HL, Chen CY 1995 Local modulation of adrenergic responses in the hindlimb vasculature of the intact conscious rat. J Physiol 485:817–825[Medline]
  42. Molinari C, Battaglia A, Bona G, Grossini E, Mary DASG, Vacca G 2000 The role of nitric oxide in the coronary vasoconstriction caused by growth hormone in anaesthetized pigs. Exp Physiol 85:203–208[Abstract]
  43. Molinari C, Grossini E, Mary DA, Ribichini F, Surico N, Vacca G 2006 The role of nitric oxide in the peripheral vasoconstriction caused by human placental lactogen in anaesthetized pigs. Exp Physiol 91:603–610[Abstract/Free Full Text]
  44. Grossini E, Molinari C, Battaglia A, Mary DA, Ribichini F, Surico N, Vacca G 2006 Human placental lactogen decreases regional blood flow in anesthetized pigs. J Vasc Res 43:205–213[CrossRef][Medline]
  45. Aggeli IK, Gaitanaki C, Lazou A, Beis I 2002 {alpha}1- and ß-adrenoceptor stimulation differentially activate p38-MAPK and atrial natriuretic peptide production in the perfused amphibian heart. J Exp Biol 205:2387–2397[Abstract/Free Full Text]
  46. Brown MA 1995 The physiology of pre-eclampsia. Clin Exp Pharmacol Physiol 22:781–791[Medline]
  47. Granger JP, Alexander BT, Bennett WA, Khalil RA 2001 Pathophysiology of pregnancy-induced hypertension. Am J Hypertens 14:178S–185S
  48. Brennecke SP, Gude NM, Di Iulio JL, King RG 1997 Reduction of placental nitric oxide synthase activity in pre-eclampsia. Clin Sci 93:51–55[Medline]
  49. Nisell H, Martinsson A, Hjemdahl P 1998 Reduced ß2-adrenoceptor sensitivity in normal pregnancy but not in pregnancy-induced hypertension. Gynecol Obstet Invest 25:262–267



This article has been cited by other articles:


Home page
 EndocrinologyHome page
E. Grossini, C. Molinari, D. A. S. G. Mary, F. Uberti, P. P. Caimmi, N. Surico, and G. Vacca
Intracoronary Genistein Acutely Increases Coronary Blood Flow in Anesthetized Pigs through {beta}-Adrenergic Mediated Nitric Oxide Release and Estrogenic Receptors
Endocrinology, May 1, 2008; 149(5): 2678 - 2687.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
148/8/4080    most recent
Author Manuscript (PDF)
Right arrow Purchase Article
Right arrow View Shopping Cart
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Molinari, C.
Right arrow Articles by Vacca, G.
Right arrow Search for Related Content