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Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
Address all correspondence and requests for reprints to: William B. Campbell, Ph.D., Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226. E-mail: wbcamp{at}mcw.edu
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Introduction |
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It is well established that the natriuretic peptides and NO have activities that lower blood pressure. The vasodilatory effects of type A natriuretic peptide and NO appear to be mediated by stimulation of guanylyl cyclase, elevation of intracellular cGMP, and activation of cGMP-dependent protein kinase (5). The similarities between type A natriuretic peptide and NO in the cardiovascular system are not limited to the vasculature. Both type A natriuretic peptide and the NO donor, sodium nitroprusside, increase cGMP production and attenuate agonist-stimulated aldosterone synthesis in adrenal zona glomerulosa cells (11, 12, 13, 14). By reducing aldosterone secretion and the aldosterone-associated retention of sodium and water, these agents may also lower blood pressure.
The regulation of aldosterone synthesis is a complex process involving the interactions of numerous modulatory substances. Angiotensin II and potassium ion are recognized as the primary physiological regulators for aldosterone synthesis (15). Recent studies also indicate the possibility of intraadrenal regulation of aldosterone synthesis through the interaction of adrenal endothelial cells and zona glomerulosa cells (16). Exposure of zona glomerulosa cells to endothelial cell-conditioned medium results in stimulation of aldosterone synthesis. This activity can be distinguished from that of any known steroidogenic agonist. The ability of the endothelial cell to produce NO (3, 4) and natriuretic peptides (17) also suggests a potential inhibitory role for the endothelium in the modulation of steroidogenesis within the adrenal gland.
Several studies have examined whether the effects of type A natriuretic peptide and NO on aldosterone synthesis are mediated by guanylyl cyclase activation. The role of guanylyl cyclase has remained questionable for at least two reasons. Previous studies have demonstrated that membrane-permeable analogs of cGMP do not mimic the effects of either type A natriuretic peptide or NO in zona glomerulosa cells (12, 14, 18, 19). Additionally, treatment with sodium nitroprusside increases the cGMP concentration in zona glomerulosa cells in all reported studies (12, 14, 18), but only attenuates steroidogenesis in one of these studies (18).
In the present study, we examined the roles of guanylyl cyclase and cGMP in mediating an inhibitory effect of NO on adrenocortical steroidogenesis. We compared the effects of type A natriuretic peptide and heat-stable enterotoxin to the effects of the NO donor, deta nonoate (ethanamine, 2,2'-(hydroxynitrosohydrazono)bis-) (20) on angiotensin II-stimulated aldosterone synthesis. Deta nonoate spontaneously dissociates by first order kinetics to equimolar concentrations of NO and ethylamine. The dissociation provides a sustained release of NO and occurs with a half-life of 56 h at pH 7.4. These studies indicated that although NO increases the cGMP content of zona glomerulosa cells, its ability to inhibit steroidogenesis is not mediated by the production of cGMP, but is instead due to the direct inhibition of steroidogenic enzymes.
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Materials and Methods |
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Aldosterone production and assay
Before the start of the experiment, adrenal zona glomerulosa
cells were washed twice with 0.5 ml steroidogenic medium 1 (SM1),
consisting of Ham’s F-12 medium, 14 mM NaCl, 14
mM NaHCO3, and 1 mg/ml BSA. Cells were
incubated in SM1 buffer for 2 h at 37 C. The buffer was then
removed and replaced with 0.5 ml steroidogenic medium 2 (SM2),
consisting of Ham’s F-12 medium, 14 mM NaCl, 14
mM NaHCO3, 1.8 mM
CaCl2, and 2 mg/ml BSA. In experiments involving the use of
antagonists, the antagonists were added 10 min before agonist addition.
The agonist or corresponding vehicle control was then added, and the
incubation was continued for 2 h at 37 C. The incubation was
stopped by transferring the SM2 buffer to plastic tubes and freezing at
-40 C for subsequent assay of aldosterone.
Aldosterone was measured by enzyme-linked immunosorbant assay (ELISA) using a mouse antialdosterone monoclonal primary antibody and aldosterone-horseradish peroxidase conjugate provided by Dr. C. E. Gomez-Sanchez (Truman V.A. Medical Center, Columbia, MO) and a goat antimouse, Fc fragment-specific secondary antibody (Jackson ImmunoResearch, West Grove, PA). The cross-reactivities of the primary antibody were as follows: aldosterone, 100%; cortisol, less than 0.0025%; corticosterone, less than 0.0025%; deoxycorticosterone, less than 0.0025%; progesterone, less than 0.0025%; 18-hydroxydeoxycorticosterone, less than 0.065%; and cortisone, less than 0.0025%. The incubation medium was assayed directly for aldosterone. ELISA 96-well plates were precoated with the secondary antibody by incubating 300 µl of a 3.3 µg/ml solution of the goat antimouse IgG in 0.1 M Na2CO3, pH 9.6, for 18 h at 4 C. The plates were then washed three times with 300 µl/well of buffer containing 135 mM NaCl, 20 mM NaH2PO4, 0.01% thimerosal, and 0.2% Tween-80 (wash buffer) using a BioTek (model EL402, Winooski, VT) automatic plate washer. Coated ELISA plates were stored in 10 mM PBS containing 138 mM NaCl and 2.7 mM KCl at 4 C until used. The aldosterone-horseradish peroxidase conjugate and antialdosterone antibody were each diluted 1:6000 in the assay buffer containing 150 mM NaCl, 100 mM NaH2PO4, 0.1% Tween-80, 0.01% thimerosal, and 0.5% BSA. The assay buffer (250 µl) was added to 50 µl of the standard or sample in each well. The assay was then allowed to equilibrate overnight at 4 C. The plates were washed six times with 300 µl/well wash buffer on an automatic plate washer, with a 1-min agitation on an orbital shaker after the third wash. The assay was developed by the addition of 0.01% urea peroxide in 100 mM citric acid and 40 mM 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid; Sigma, St. Louis, MO) as a color reagent. Aldosterone was quantified by colorimetric measurement using a Bio-Tek model EL309 automated plate reader with a 490-nm filter. Pregnenolone was measured by RIA as previously described (21). Data represent averages of multiple incubations from at least two cell preparations or are from a representative experiment from multiple cell preparations. To compensate for variations in aldosterone production between zona glomerulosa cell preparations, angiotensin II (1 nM) was included as a positive control in each experiment.
cGMP production and assay
Zona glomerulosa cells and T84 cells were cultured as previously
described. The cell wells were rinsed twice with 0.5 ml SM1 and allowed
to incubate for 2 h at 37 C. During the final 10 min of this
incubation, the cells were treated with 0.25 mM
isobutylmethylxanthine (IBMX) as well as any inhibitors or vehicle
controls required for the experiment. The SM1 was subsequently removed
and replaced with 0.5 ml SM2 containing identical concentrations of
IBMX and inhibitors. The agonists and vehicle controls were added, and
the incubation was continued for 15 min at 37 C. To terminate the
reaction, the SM2 was removed and replaced with 0.5 ml 1 M
perchloric acid, after which the plates were rapidly frozen at -80 C.
Plates were stored at -80 C until assayed for cGMP concentration.
cGMP in the sample was purified by alumina and Dowex anion exchange chromatography and quantitated by RIA as described previously (22). The anti-cGMP serum was prepared in our laboratory. A 2'-O-succinyl derivative of cGMP (Sigma) was purified by HPLC, and its purity and identity were verified by nuclear magnetic resonance imaging. It was conjugated to thyroglobulin by the mixed anhydride method (23). cGMP (13.7 µmol) was dissolved in dioxane (0.5 ml) and incubated for 20 min at 4 C with an equimolar amount of ethylchloroformate and twice the molar amount of triethylamine. It was added dropwise to 30 mg porcine thyroglobulin dissolved in 0.5 ml 0.1 M sodium carbonate, and the mixture was incubated for 4 h at 4 C. The conjugate was then dialyzed and stored in aliquots at -80 C. Rabbits were injected monthly with 0.25 mg of the conjugate in Freunds adjuvant (Life Technologies, Gaithersburg, MD) at multiple intradermal and sc sites. On the sixth day after immunization, blood was collected from the center ear artery, and serum was harvested. The antiserum was used at a final titer of 1:20,000, which binds approximately 50% of [125I]cGMP. This antibody had the following cross-reactivities with related compounds: cAMP, 0.02%; 5'-AMP, less than 0.0001%; 3'-AMP, less than 0.0001%; ATP, less than 0.0001%; GTP, less than 0.0001%; 5'-GMP, less than 0.004%; and 3'-GMP, 0.0002%. The sensitivity of the antibody was 3 fmol/tube. Normal standard curves included amounts ranging from 5–1,000 fmol/tube.
Preparation of zona glomerulosa mitochondria
Adrenal glands were trimmed of fat and placed in ice-cold buffer
consisting of 10 mM Tris-HCl, 250 mM sucrose,
and 1 mM EDTA, pH 7.5 (buffer A). Glands were bisected and
sectioned on a Stadie-Riggs microtome. The sections were finely minced
and homogenized with a motor-driven Teflon pestle homogenizer. The
homogenate was centrifuged at 900 x g for 10 min at 4
C. The supernatant was decanted into a chilled 50-ml centrifuge tube
and centrifuged at 9000 x g for 10 min at 4 C. This
supernatant was discarded, and the mitochondrial pellet was saved and
resuspended in cold buffer A. The mitochondrial suspension was again
centrifuged at 9000 x g. The final pellet was
resuspended in a small volume of buffer containing 10 mM
Tris-HCl, 250 mM sucrose, 20 mM KCl, 10
mM K2HPO4, 5 mM
MgCl2, 10 µM cyanoketone, and 0.2% BSA, pH
7.5 (buffer B). The protein concentration of this suspension was
determined using the Bio-Rad (Hercules, CA) protein assay and was
diluted to a final protein concentration of 1 mg/ml in buffer B.
Ten-milliliter aliquots of the mitochondrial suspension in 50-ml
conical centrifuge tubes were placed in a 22 C shaking water bath. Deta
nonoate (500 µM or 1 mM) or its vehicle
control was added to each tube and incubated at 22 C for 30 min. The
enzymatic reaction was started with the addition of 10 mM
isocitrate and 1 µg/ml 25-hydroxycholesterol to the mitochondrial
suspension. Three 500-µl samples were removed from each flask at 0,
1, 5, and 20 min and vortexed with 3 ml dichloromethane in a 15-ml
glass tube. The dichloromethane layer was removed, placed in a clean
tube, and dried under vacuum. Pregnenolone was quantified by
resuspending the dried samples in 500 µl buffer B and assaying by RIA
as indicated above.
Spectrophotometry of cytochrome P450 enzymes
Mitochondria were prepared as described above and resuspended at
a protein concentration of 0.5–1 mg/ml. The suspension was treated
with a few grains of sodium dithionite to reduce the heme iron and then
placed into two cuvettes in a SLM/Aminco DW2000 (Urbana, IL) UV/visible
light spectrophotometer to obtain the baseline. The sample cuvette was
bubbled with 100% carbon monoxide and/or treated with deta nonoate
(10-6-10-3 M), and the difference
spectrum was immediately recorded. A fresh suspension of mitochondria
was prepared in an identical manner, and the order of addition was
reversed (i.e. deta nonoate before carbon monoxide). All
spectra were collected repetitively, with successive scans separated by
2–5 min. Final difference spectra were analyzed after subtraction of
the baseline. The results are typical tracings of stabilized spectra.
Spectra were considered stabilized when there was no change in spectral
shape between two successive scans.
All statistical analysis was performed using ANOVA followed by paired t test. P < 0.05 was considered statistically significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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) and deta nonoate
(10-6-10-3 M; Fig. 1B) increased
cGMP in a concentration-dependent manner. These type A natriuretic
peptide- and deta nonoate-mediated increases in cGMP production are
consistent with the presence of guanylyl cyclase A and soluble guanylyl
cyclase, respectively, in zona glomerulosa cells. The ability of the
soluble guanylyl cyclase inhibitor
1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) to block
NO-stimulated cGMP production was also tested in these experiments. ODQ
(10-5 M) completely blocked the deta
nonoate-induced increase in cGMP production at all concentrations of
the NO donor. Unlike deta nonoate, the type A natriuretic
peptide-induced increase in cGMP was not inhibited by ODQ, indicating
that the inhibitor is specific for the soluble form of guanylyl
cyclase.
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Effects of type A natriuretic peptide, deta nonoate,
and heat-stable enterotoxin on angiotensin II-evoked aldosterone
synthesis
Similar studies examined the effects of these agonists on
aldosterone release. Angiotensin II (1 nM) was used to
stimulate aldosterone release. Type A natriuretic peptide
(10-10-10-6 M) and deta nonoate
(10-6-10-3 M) inhibited
angiotensin II (1 nM)-stimulated aldosterone release in a
concentration-related manner (Fig. 2, A
and B, respectively). Heat-stable enterotoxin did not affect basal or
angiotensin II-stimulated steroidogenesis (control, 0.40 ± 0.04
pg/µg protein; heat-stable enterotoxin treatment alone, 0.30 ±
0.05 pg/µg protein; angiotensin II alone, 5.78 ± 0.07 pg/µg
protein; angiotensin II- and heat-stable enterotoxin treatment,
5.71 ± 0.09 pg/µg protein; n = 4). The experiments were
repeated in the presence of ODQ to determine the involvement of cGMP in
the inhibition of aldosterone production. ODQ (10-5
M) pretreatment did not effect angiotensin II-stimulated
aldosterone production (Fig. 2). ODQ blocked the inhibitory effect of
deta nonoate on angiotensin II-stimulated aldosterone production at the
10-6-M concentration of the NO donor, but was
ineffective at higher concentrations of the NO donor (Fig. 2B). ODQ did
not block the ability of type A natriuretic peptide to inhibit
angiotensin II-stimulated steroidogenesis (Fig. 2A). Interestingly, the
inhibition by type A natriuretic peptide was greater in the presence of
ODQ. This synergistic effect of ODQ and type A natriuretic peptide is
currently unexplained. These data indicated that NO stimulation of
soluble guanylyl cyclase and the subsequent generation of cGMP were not
required for NO inhibition of aldosterone production.
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Effects of type A natriuretic peptide and deta nonoate on
25-hydroxycholesterol-stimulated aldosterone release
Addition of 25-hydroxycholesterol (0.4–40 µM)
resulted in a concentration-dependent increase in aldosterone
synthesis. This stimulation by 25-hydroxycholesterol was unaffected by
10-6 M type A natriuretic peptide treatment
(Fig. 3A), but was completely blocked by
10-3 M deta nonoate (Fig. 3B). ODQ
pretreatment did not block the effect of deta nonoate. These data
indicated that the inhibition of aldosterone production by NO occurs at
some point after the mobilization of cholesterol and does not involve
cGMP. We next examined the effect of NO on a later step in aldosterone
production by providing the substrate progesterone.
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). This stimulation was inhibited by
10-6 M deta nonoate and was completely blocked
by deta nonoate in concentrations from
10-5–10-3 M (Fig. 4B). This
suggests that NO directly interferes with one or more of the enzymes
necessary for the conversion of 25-hydroxycholesterol and progesterone
to aldosterone. Isolated zona glomerulosa mitochondria were used to
examine the effect of NO on the conversion of cholesterol to
pregnenolone by the cytochrome P450 side-chain cleavage enzyme.
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). Deta
nonoate (5 x 10-4 and 1 x 10-3
M) reduced the conversion of 25-hydroxycholesterol to
pregnenolone over the 20 min of incubation. These data indicate
inhibition of the cytochrome P450 side-chain cleavage enzyme by NO.
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, tracing A. A typical
difference spectrum after carbon monoxide treatment for the zona
glomerulosa mitochondria is shown in Fig. 6A, tracing C. The Soret
maximum was at 450 nm. Deta nonoate treatment produced a spectrum that
differed from that produced by carbon monoxide treatment. The spectrum
shifted to a Soret maximum at 453 nm with deta nonoate (Fig. 6A, tracing B). The carbon monoxide spectrum was not affected by the
subsequent addition of deta nonoate (Fig. 6A, tracing D). Similarly,
the deta nonoate spectrum was only slightly affected by subsequent
carbon monoxide treatment (Fig. 6A, tracing E). This finding indicates
that pretreatment with deta nonoate prevents carbon monoxide from
binding to the heme sites of the mitochondrial cytochrome P450 enzymes
and suggests a direct NO interaction with the heme. This effect was
further examined with varying concentrations of deta nonoate (Fig. 6B).
Suspensions treated with vehicle or 1 µM deta nonoate
demonstrated a characteristic peak at 450 nm due to carbon monoxide
heme binding. At deta nonoate concentrations of 10 µM and
greater, the 450-nm peak was reduced or eliminated. These data indicate
that deta nonoate concentrations of 10 µM to 1
mM inhibit the binding of carbon monoxide to the cytochrome
P450 heme sites.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The potential involvement of guanylyl cyclases in adrenocortical steroidogenesis was also examined using heat-stable enterotoxin, an agonist for the particulate guanylyl cyclase C (5). A previous report suggested that guanylyl cyclase C was expressed in adrenal tissue (25). In the present study, heat-stable enterotoxin failed to increase cGMP production or inhibit basal or angiotensin II-induced aldosterone synthesis in zona glomerulosa cells. This lack of effect was not due to inactive toxin or species insensitivity, as heat-stable enterotoxin stimulated cGMP production in a human colonic T84 cell line, and heat-stable enterotoxin has been shown to be biologically active in the intestines of domestic cattle (26). These data suggest that guanylyl cyclase C is absent in zona glomerulosa cells. The previous identification of guanylyl cyclase C messenger RNA in the adrenal gland (25) may therefore be explained by the possibility that the receptor is expressed in medulla or other nonsteroidogenic cells or that the transcript is not effectively translated in adrenocortical tissue.
Previous studies have examined the effects of NO on adrenocortical steroidogenesis. These investigators found that sodium nitroprusside increased cGMP production over a brief time course of 5–10 min (12, 14, 18). In one of these three studies, sodium nitroprusside was reported to attenuate aldosterone synthesis at high concentrations (18). The steroidogenesis experiments in these studies were performed for 1–2 h in the presence of sodium nitroprusside. The mixed results with sodium nitroprusside on steroidogenesis may be due to the short half-life of this NO donor, which degrades in solution within minutes. In the current study, our incubations were performed for 2 h, using a NO donor with a 56-h half-life (20). The relatively long half-life of deta nonoate provides a consistent NO release throughout the incubation period. However, the long half-life also requires the addition of high concentrations of deta nonoate to generate relatively low concentrations of NO. The addition of 1 mM deta nonoate results in a steady state NO concentration of approximately 40 nM during the course of a 2-h incubation.
Deta nonoate reduced angiotensin II-stimulated aldosterone synthesis in a concentration-dependent manner. The effect of deta nonoate at concentrations of 10-5 M and greater was associated with measurable increases in intracellular cGMP. Pretreatment with ODQ abolished the production of cGMP by deta nonoate but had no effect on nonoate-mediated inhibition of aldosterone. This observation indicates that deta nonoate is capable of attenuating steroidogenesis independent of guanylyl cyclase activation. The ability of ODQ to block the effect of 10-6 M nonoate on steroidogenesis may argue that the effects of low concentrations of NO may be mediated by soluble guanylyl cyclase. This concentration of deta nonoate was also unable to block carbon monoxide binding in isolated mitochondria. However, 10-6 M deta nonoate did not measurably increase cGMP concentrations in the same cells. The ability of NO to inhibit aldosterone production independent of cGMP synthesis raised the possibility that NO may have direct effects on the steroidogenic enzymes.
The effect of NO was tested on the aldosterone release stimulated by 25-hydroxycholesterol. This steroid crosses cell membranes, acts as a substrate for aldosterone biosynthesis, and bypasses both signal transduction mechanisms and protein mediators such as steroidogenic acute regulatory protein, associated with cholesterol mobilization. Deta nonoate blocked 25-hydroxycholesterol-stimulated aldosterone synthesis. This finding is consistent with a direct effect of NO on one or more of the steroidogenic enzymes and indicates that the effect is independent of soluble guanylyl cyclase activation. Type A natriuretic peptide was without effect on 25-hydroxycholesterol-stimulated aldosterone production, which is consistent with the involvement of a receptor-mediated signaling cascade involving particulate guanylyl cyclase and cGMP production in the action of this peptide (19, 27). Deta nonoate was additionally found to inhibit the conversion of exogenous progesterone to aldosterone, consistent with an inhibitory effect of NO on steroidogenic enzymes, possibly CYP21 and/or CYP11B2.
Previous studies indicate that NO affects testosterone synthesis by
direct effects on the enzymes involved in steroidogenesis (28). To
examine this possibility for aldosterone synthesis, we used an isolated
mitochondrial fraction from the zona glomerulosa layer of the adrenal
cortex and tested the ability of deta nonoate to block a single
enzymatic step, the conversion of 25-hydroxycholesterol to
pregnenolone. The experiment was performed in the presence of
cyanoketone (10 µM), an inhibitor of
3ß-hydroxy-
5-steroid dehydrogenase, to block further
conversion of pregnenolone to progesterone (29). This assay provides a
direct measure of the activity of the cytochrome P450 side-chain
cleavage enzyme in the absence of any signal transduction pathways.
Deta nonoate blocked the enzymatic conversion of cholesterol to
pregnenolone, indicating an inhibition of the cytochrome P450
side-chain cleavage enzyme. This finding should not be interpreted to
indicate that the cholesterol side-chain cleavage enzyme is the only
site of NO inhibition. Deta nonoate also blocked later steps, such as
the metabolism of progesterone to aldosterone in intact cells. The
ability of NO to inhibit members of the cytochrome P450 family is not
limited to steroidogenic enzymes. In a recent study, nonoates were
found to inhibit the hepatic CYP2E1 (30). Previous reports have
demonstrated that NO donors inhibit the hepatocellular CYP1A1, CYP1A2,
and CYP2B1 (31, 32, 33). Therefore, the inhibitory effect of NO on these
enzyme isoforms is likely to be nonselective, similar to that of carbon
monoxide.
The difference spectra for total mitochondrial cytochrome P450 enzymes was shifted by deta nonoate. Furthermore, deta nonoate interfered with the ability of carbon monoxide to induce its characteristic spectral peak at 450 nm, suggesting that NO and carbon monoxide compete for binding to the heme group of the cytochromes. The inability of carbon monoxide to produce its typical spectra in the presence of 10 µM to 1 mM deta nonoate further suggests that the majority of cytochrome P450 enzymes in the mitochondrial suspension were already bound by NO before carbon monoxide treatment. The high affinity of NO for the heme group is emphasized by the ability of 10 µM deta nonoate to inhibit the binding of saturating concentrations of carbon monoxide and by 10 µM deta nonoate representing a steady state NO concentration of approximately 400 pM. This further supports a nonspecific interaction between NO and all of the mitochondrial cytochrome P450 enzymes in the mitochondrial suspension. In rat liver microsomes, Gergel et al. (30) found that nonoates not only inhibited CYP2E1 but also induced a shift of the cytochrome P450 spectrum. Nonoates also prevented carbon monoxide from inducing its characteristic spectral shift, similar to the results of the present study.
This study indicates that NO inhibits aldosterone synthesis independent of guanylyl cyclase activation and through a direct inhibition of several cytochrome P450 steroidogenic enzymes. From the results of this study, we cannot rule out the possibility of guanylyl cyclase-mediated inhibition of steroidogenesis. NO may be capable of inhibiting aldosterone release by increasing cGMP; however, this effect is overwhelmed by the more direct and distal effect to inhibit the steroidogenic enzymes. Thus, the effect of NO on signal transduction is masked by the more distal effects on steroidogenesis. The ability of type A natriuretic peptide in the present study to increase cGMP production and reduce aldosterone synthesis argues that guanylyl cyclase and cGMP affect steroidogenesis.
The ability of deta nonoate to inhibit aldosterone synthesis at multiple steps along the biosynthetic pathway suggests that locally produced NO within the adrenal gland could be an effective means of regulating aldosterone production. The steady state concentrations of NO necessary for the inhibition of aldosterone production in this study were in the high picomolar or low nanomolar range. Stimulation of NO synthesis in endothelial cells may, therefore, be a vehicle for both immediate antihypertensive action through vasodilation and a sustained antihypertensive effect through the inhibition of aldosterone synthesis. The role of the adrenal endothelium may be to fine-tune aldosterone production through the localized secretion of a stimulatory factor (16) and inhibitory modulators such as NO.
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Acknowledgments |
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Footnotes |
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Received June 23, 1998.
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References |
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-type-A natriuretic peptide on aldosterone
inhibition. Am J Physiol 252:E643–E647
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C. J. Hanke and W. B. Campbell Endothelial cell nitric oxide inhibits aldosterone synthesis in zona glomerulosa cells: modulation by oxygen Am J Physiol Endocrinol Metab, October 1, 2000; 279(4): E846 - E854. [Abstract] [Full Text] [PDF]
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 J. J. Jaroszewski and W. Hansel Intraluteal Administration of a Nitric Oxide Synthase Blocker Stimulates Progesterone and Oxytocin Secretion and Prolongs the Life Span of the Bovine Corpus Luteum Experimental Biology and Medicine, May 1, 2000; 224(1): 50 - 55. [Abstract] [Full Text]
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 C. L. Coulter, D. A. Myers, P. W. Nathanielsz, and I. M. Bird Ontogeny of Angiotensin II Type 1 Receptor and Cytochrome P450c11 in the Sheep Adrenal Gland Biol Reprod, March 1, 2000; 62(3): 714 - 719. [Abstract] [Full Text]
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C. J. Hanke, T. O'Brien, K. A. Pritchard Jr, and W. B. Campbell Inhibition of Adrenal Cell Aldosterone Synthesis by Endogenous Nitric Oxide Release Hypertension, January 1, 2000; 35(1): 324 - 328. [Abstract] [Full Text] [PDF]
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L. J. Rosolowsky, C. J. Hanke, and W. B. Campbell Adrenal Capillary Endothelial Cells Stimulate Aldosterone Release through a Protein That Is Distinct from Endothelin Endocrinology, October 1, 1999; 140(10): 4411 - 4418. |
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P < 0.05; 
