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Division of Endocrinology, Departments of Medicine (J.Q., S.M., T.N., J.A.F., T.L.C.) and Molecular and Cellular Physiology (R.L.S., J.N.L., C.W., R.J.P., J.A.F., T.L.C.), University of Cincinnati (S.M., J.Q., R.L.S., J.N.L., J.W., H.T., T.N., C.W., R.J.P., J.A.F., T.L.C.), and the Department of Pathology (D.W.), Children’s Hospital, Cincinnati, Ohio 45267; and the Department of Cell Biology, Neurobiology, and Anatomy, Ohio State University (A.R.S.), Columbus, Ohio 43210
Address all correspondence and requests for reprints to: Thomas L. Clemens, Ph.D., Division of Endocrinology and Metabolism, University of Cincinnati, Room 5564, 231 Bethesda Avenue, Cincinnati, Ohio 45267-0547. E-mail: clementl{at}uc.edu
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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-actin promoter to direct expression of the
transgene. In the PTHrP-overexpressing mice, messenger RNA expression
was mainly restricted to smooth muscle-containing tissues. Several
founders also expressed the transgene in bone and heart and exhibited
striking abnormalities in the development of these tissues. In
PTHrP-overexpressing mice, blood pressure was significantly lower than
that in wild-type controls (121 ± 3 vs. 135
± 2 mm Hg; P < 0.01). Moreover, the magnitude of
the vasorelaxant response to iv infusions of
PTHrP-(1–34)NH2 was significantly attenuated in the
transgenic animals. A similar desensitization to PTHrP was observed in
aortic ring and portal vein preparations. Surprisingly,
PTHrP-overexpressing mice were also significantly less responsive to
the hypotensive action of infused acetylcholine in vivo
and to the relaxant actions of acetylcholine on aortic vessel
preparations in vitro. In summary, we have successfully
targeted overexpression of PTHrP to the smooth muscle of transgenic
mice. When expressed in its normal autocrine/paracrine setting, PTHrP
lowers systemic blood pressure and decreases vascular responsiveness to
further relaxation by PTHrP and other endothelium-dependent
vasorelaxants such as acetylcholine. We postulate that the heterologous
desensitization to acetylcholine-induced relaxation in
PTHrP-overexpressing blood vessels involves desensitization of second
messenger/effector signaling pathways common to PTHrP and
acetylcholine. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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There is increasing evidence supporting a role for PTHrP in the control of vascular tone. PTHrP is expressed in blood vessels from a wide array of vascular beds, including rat aorta (5, 6), vena cava (5), kidney microvessels (7), arterial and venous supplies of the mammary gland (8), and serosal arterioles of the avian egg shell gland (9). The protein has also been detected in many fetal blood vessels (10, 11). In most if not all of these vessels PTHrP appears to be expressed in the smooth muscle layer. Exogenous application of synthetic PTHrP peptides exert relaxant activity on both conductance and resistance vessels from different species (12). Cultured arterial vascular smooth muscle cells express both PTHrP (13) and the type 1 PTH/PTHrP receptor (14). In addition, PTHrP production by cultured vascular smooth muscle cells is stimulated by vasoconstrictor agents such as angiotensin II (15), suggesting the existence of a short feedback loop through which the local vasorelaxant actions of PTHrP function to oppose pressor activity of angiotensin II and other vasoconstrictor agents. However, the biology of locally produced PTHrP in vascular or other smooth muscle beds has not previously been examined in vivo.
Transgenic models have recently been used to explore the autocrine/paracrine functions of locally produced PTHrP in the development of several organ systems in vivo. For example, transgenic mice with targeted overexpression of PTHrP in skin show marked disturbances in hair follicle development (16). In this same model, the targeting promoter (keratin 14) also directed PTHrP overexpression in myoepithelial cells of breast ductules, which resulted in failure of lactation in female transgenic mice (17). By contrast, the lack of PTHrP or its receptor in knockout mice demonstrated the importance of this peptide in chondrocyte differentiation (18, 19); both PTHrP and the PTH/PTHrP receptor knockouts are lethal and are associated with premature terminal differentiation and calcification of chondrocytes.
The object of the present studies was to determine the effects of locally produced PTHrP on vascular contractility by targeting its overexpression to smooth muscle of transgenic mice. Mice overexpressing PTHrP in vascular smooth muscle demonstrated a reduced systemic blood pressure compared with their wild-type littermates. Interestingly, the local overexpression of PTHrP also desensitized vascular beds to acetylcholine and sodium nitroprusside (SNP), suggesting heterologous desensitization of a common second messenger/effector pathway(s).
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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-actin gene (SMP8) containing
1074 bp of the 5'-flanking region, the 63-bp 5'-untranslated and 2.5-kb
first intron, and 15 bp of exon 2 (20) to the human PTHrP
complementary DNA (cDNA) (21) followed by the simian virus 40 early
polyadenylation signal fragment (Fig. 1
).
The SMP8-PTHrP fusion gene was released from pSMP8-PTHrP by
EcoRI and SphI restriction before microinjection.
The male pronuclei of fertilized eggs from FVB/N mouse strains were
microinjected with 2 pl linearized DNA at the transgenic mouse facility
of the University of Cincinnati. Microinjected eggs were implanted into
the oviduct of pseudopregnant female mice and carried to term. Positive
founders were identified by Southern blotting and were bred to
wild-type FVB/N mice for propagation of the line. Heterozygotes and
wild-type progeny from the F1 and subsequent generations
were selected by Southern blotting of EcoRI-restricted
genomic DNA. Hybridization was performed with a human PTHrP cDNA
labeled by random priming (Prime-It II kit, Stratagene, La
Jolla, CA). The transgene was identified as a unique 1.1-kb band. All
animals received humane care in compliance with the local institutional
animal care and use committee.
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Tissue histology and morphometry
Transgenic mice and their wild-type littermates were killed by
CO2 asphyxiation. After determining the body weight, blood
was collected by cardiac puncture, and serum was stored at -80 C until
assay. Organs of interest were dissected, rinsed in ice-cold PBS,
tissue-blotted, weighed, and immediately frozen in dry ice. Morphometry
was performed using NIH Image version 1.61, an image-processing and
analysis program for the Macintosh computer. The arterial
section images of SMP8-PTHrP transgenic mice (line 375) and their
age-matched wild-type controls were color-captured into the computer
from Trichrome-stained sections through the microscope. After adjusting
the image contrast, the area of interest was autooutlined, and the
regions outside and inside the area were cleared as previously
described (20). Cranial bone was fixed in 10% formalin-PBS (pH 7.4) at
4 C and decalcified in 10% formalin-PBS (pH 7.4) containing 20% EDTA.
Paraffin blocks were prepared by standard histological procedures.
Sections (5–6 µm thickness) were cut at several levels and stained
with hematoxylin and eosin.
In situ hybridization
In situ hybridization was performed as previously
described (22). Briefly, tissues dissected from animals at the
indicated ages were fixed in 4% paraformaldehyde, saturated overnight
with 30% sucrose in PBS, and frozen in M-1 (Lipshaw, Pittsburgh, PA).
Cryostat sections (7 µm) were mounted on silane-coated slides. An
antisense complementary RNA probe for human PTHrP was labeled with
[35S]recombinant UTP using a commercially
available kit (Stratagene, La Jolla, CA). For generation
of the antisense PTHrP riboprobe, a PvuII to SacI
fragment corresponding to nucleotides +230–537 of the human PTHrP cDNA
(21) was cloned into the pBluescript SK(+) plasmid, linearized with
EcoRI, and transcribed with T3 RNA polymerase. Hybridization
was performed with a total of 1 x 106 cpm in a final
volume of 30 µl/slide. The sections were hybridized overnight at 42
C, treated with 50 µg/ml ribonuclease A (Sigma Chemical Co., St. Louis, MO) and 100 U/ml ribonuclease T1
(Boehringer Mannheim, Indianapolis, IN) for 30 min at 37
C, and washed to a final stringency of 0.1 x standard citrate
saline at 50 C. Slides were dipped in NTB2 emulsion (Eastman Kodak Co., Rochester, NY), diluted 1:1 with 0.6 mol/liter
ammonium acetate, exposed for 10–14 days, and developed in D19
developer (Eastman Kodak Co.). Sections were photographed
under darkfield illumination.
Noninvasive blood pressure measurements
After a 5-day training period, daily blood pressure measurements
were performed in conscious mice over a 5-day period using a
computerized tail-cuff system (Visitech Systems, Apex, NC). Animals
were placed in a Lucite restrainer with their tails protruding from a
small opening in the back. A balloon cuff was placed over the proximal
portion of the tail, and a more distal portion of the tail was draped
over a photoelectric sensor for detecting blood flow. For 10
consecutive cycles, the balloon cuff was inflated by a small air pump
until detectable blood flow in the tail ceased; this pressure was taken
as the end point. The cuff was then immediately deflated, and the next
cycle was started 10 sec later. In each trial, the 10 measurement
cycles were preceded by 10 preliminary cycles to acclimatize the mice
to the apparatus.
Measurement of mean arterial pressure and cardiac output in intact
mice
The surgical preparation for determining circulatory parameters
in the intact mouse was adapted from that described previously in
detail (23). In brief, mice were anesthetized with an ip injection of
ketamine (50 µg/g BW) and inactin (100 µg/g BW; Research Biochemicals International, Natick, MA). The right femoral
artery and vein were cannulated with hand-drawn polyethylene tubing
(o.d., 
0.3 mm) for the measurement of arterial pressure and the
infusion of experimental agents. The arterial catheter was connected to
a low compliance transducer (COBE CDXIII, Arvada, CO), and amplified
pressure signals were recorded using a MacLab 4/s data acquisition
system at a sampling rate of 1000 samples/sec. A 0.5-mm catheter
custom fashioned with a 20-MHz Doppler crystal at the tip was then
inserted into the right carotid artery and advanced to its junction
with the ascending aorta. The catheter was connected to a Millar MDV-20
pulsed Doppler velocimeter (Houston, TX), and signals for phasic and
mean flow were recorded as an estimate of cardiac output. The position
of the catheter was constantly adjusted so as to obtain a maximum value
for peak aortic blood flow velocity. We have previously demonstrated
that the phasic and mean signals from the Doppler crystals closely
reflect those obtained simultaneously from a bulk flow meter positioned
around the ascending aorta in the opened chest mouse (unpublished
observation). In addition, the values obtained for peak and mean flow
velocity using the pulsed Doppler approach are consistent with other
measurements of cardiac output in the mouse (24, 25). Beat to beat
values for mean arterial pressure and mean aortic blood flow velocity
were used to calculate a tracing of total peripheral resistance with
the units millimeters per Hg/cm·sec. All data were analyzed using a
two-factor ANOVA, with repeated measures on the second factor.
Comparisons of individual means were performed using individual
contrasts.
Dose-response relationships for PTHrP and acetylcholine were determined in each group of animals by infusing increasing concentrations of these peptides, dissolved in saline, at a constant rate of 0.1 µl/min·g BW for 3 min. Average reported values for each variable were calculated from a 20-sec period occurring at the maximum response of TPR for each dose. The animal was allowed to recover fully for a 10- to 15-min period before administration of each subsequent dose.
Analysis of blood vessel contractile properties
Blood vessel contractile properties were analyzed as described
previously (26, 27) with modifications. Briefly, 9-week-old FVB/N mice
and age-matched SMP8-PTHrP transgenic mice were killed in a charged
CO2 chamber. Segments of thoracic aorta (5–7 mm) were
dissected and mounted for isometric force recording as previously
described (26). The portal vein was dissected from the mouse by tying a
4–0 suture at the two ends of the vessel (between the hepatic
bifurcation and the anterior mesenteric vein). The portal vein was cut
free, and each end was secured with its thread to the myograph. From
the time of dissection the vessel was maintained in a physiological
salt solution containing 118 mmol/liter NaCl, 4.73 mmol/liter KCl, 1.2
mmol/liter MgCl2, 0.026 mmol/liter EDTA, 1.2 mmol/liter
KH2PO4, 2.5 mmol/liter CaCl2, and
5.5 mmol/liter glucose buffered with 25 mmol/liter
NaH2CO3 that when bubbled with 95%
O2-5% CO2 was pH 7.2 at 37 C. Experiments were
conducted at optimal tension by adjusting the length of the vessels to
a point where maximum peak to peak oscillations were observed. Force
measurements were obtained using a Harvard Apparatus differential
capacitor force transducer (South Natick, MA), which was connected to a
Biopac MP100 data acquisition system. Data from
concentration-response curves were compared using two-way ANOVA.
Significance was defined as P < 0.05 for all
tests.
Peptides
Synthetic PTHrP-(1–34)NH2, acetylcholine, and
phenlyephrine were purchased from Bachem California, Inc.
(Torrance, CA). Peptides were stored at -20 C in 0.01 N
acetic acid. SNP was purchased from Sigma Chemical Co.
(St. Louis, MO).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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). The
difficulty in obtaining viable mice overexpressing PTHrP in smooth
muscle together with the variable phenotypes of the founders obtained
indicate that high level expression of PTHrP in critical tissues
disrupts development and in some cases causes embryonic death.
F1 offspring from an additional line (375) exhibited no
obvious outward phenotype and expressed high levels of PTHrP messenger
RNA (mRNA) in smooth muscle. These mice were therefore propagated for
study of the effects of PTHrP overexpression on their cardiovascular
function.
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. Endogenous PTHrP mRNA was present at
low levels in bladder and stomach, but was undetectable in other
tissues. The PTHrP transgene, identified because of its slightly
smaller size (1.1 kb) compared with the endogenous PTHrP mRNA (1.4 kb),
was detected at very high levels in bladder, stomach, uterus, and aorta
and to a lesser degree in intestine. Figure 3B shows a Northern blot
subjected to phosphorimaging for an extended period to assess the
relative expression of transgenic PTHrP mRNA in different tissues of
two individual SMP8-PTHrP transgenic mice. In the mouse from line 375,
transgenic mRNA was expressed at high levels in smooth muscle and at
lower levels in heart. The mouse from line 368 that exhibited the bone
phenotype described above expressed comparatively higher levels of the
transgene in bone and heart.
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). Transgene mRNA expression was
largely confined to smooth muscle, including the smooth muscle cell
layers of the intestine, aorta, bladder, stomach, bronchus, pulmonary
artery, uterus, and meningeal and renal arterioles. The PTHrP transgene
was also expressed in the stromal cells of the lamina propria of the
gut, which are known to express endogenous smooth muscle -actin
(29).
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). For unexplained reasons, total
body and carcass weights of female transgenic mice were significantly
lower than those of their wild-type littermates. These differences
tended to diminish with advancing age. Even after adjusting for body
weight, intestinal weight was decreased at both 9 and 13 weeks of age,
whereas stomach weight was greater in 13-week-old male and female
transgenic mice. There were no major differences in the weights of any
other organs (Table 1).
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Effects of overexpression of PTHrP on blood pressure and
hemodynamics in the whole animal
We next investigated whether overexpression of PTHrP influenced
cardiovascular hemodynamics in the intact mouse. Blood pressure was
evaluated for 5 days by tail cuff sphygmomanometry in four wild-type
and six transgenic littermates. Blood pressure was significantly lower
in the transgenic animals compared with that in wild-type mice
(121 ± 3 vs. 135 ± 2 mm Hg; P <
0.01). Cardiovascular hemodynamic measurements were also made in
anesthetized, closed chest mice, as shown in Fig. 5. In contrast to the results obtained in
conscious mice, baseline blood pressure did not differ significantly
between the two groups. Baseline mean velocity and peripheral
resistance were also similar in the two groups. The lack of a
difference in baseline blood pressure and total peripheral resistance
in transgenic and wild-type anesthetized mice may relate in part to the
decreased sympathetic tone induced by the anesthesia, which could have
obscured any further reduction in pressure by local overexpression of
PTHrP.
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Because the ability of PTHrP to maximally relax murine aorta requires the presence of an intact endothelium (31), we investigated the possibility that local overexpression of PTHrP would also alter relaxation responses to other vasodilators that act through endothelium-dependent mechanisms. Acetylcholine was infused over a 30-min period at stepwise dose increments ranging from 0.3 ng/ml to 0.3 mg/ml. The maximal change in pressure in response to acetylcholine infusions was also blunted in animals overexpressing PTHrP. At the highest dose, acetylcholine decreased blood pressure by 51.7 ± 4.8 mm Hg in the wild-type animals and by only 33.1 ± 5.3 mm Hg in the transgenic mice. Again, peripheral resistance mirrored pressure changes; mean changes were 5.3 ± 0.8 mm Hg/cm·sec in the wild-type and 3.8 ± 0.2 mm Hg/cm·sec in the transgenic mice.
Effects of overexpression of PTHrP on vascular contractility
To further investigate the effect of overexpression of PTHrP on
vascular tone, we analyzed the contractile properties of PTHrP in aorta
and portal vein preparations from 9-week-old mice. Aortic rings from
transgenic and wild-type mice, isometrically mounted in the same bath,
were precontracted with 1 µM phenlyephrine, a
concentration that produced an 80% maximal contraction. There was no
significant difference in the maximal force of contraction elicited by
phenlyephrine in transgenic vs. wild-type aortas (Fig. 6A). A similar result was obtained when
the vessels were precontracted by depolarization with KCl (not shown).
In aortas from wild-type mice, PTHrP-(1–34)NH2 produced
marked relaxation responses, whereas there was no effect on aortas from
PTHrP-overexpressing mice (Fig. 6A). Relaxation-response curves were
generated using a single concentration of PTHrP per aorta, because
addition of a single dose of PTHrP-(1–34)NH2 was
associated with desensitization to subsequent doses of PTHrP (Fig. 6B).
Consistent with the in vivo results,
PTHrP-(1–34)NH2 produced a dose-dependent relaxation of
wild-type mouse aortas, but had virtually no relaxant effect on the
aortas from the PTHrP-overexpressing mice, even at concentrations as
high as 100 nM. This finding suggests that the local
overexpression of PTHrP resulted in desensitization of the aorta to
PTHrP. A similar phenomenon was observed in the portal vein. PTHrP
induced dose-dependent relaxation of spontaneous contractions in both
transgenic and wild-type mouse portal vein (Fig. 7). Comparison of the
concentration-response relationships revealed that portal veins from
PTHrP-overexpressing mice were more resistant to PTHrP-induced
relaxation than those from wild-type counterparts.
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). The
EC50 values were 7.9 ± 1.1 and 33 ± 2
nM for wild-type and transgenic mice, respectively.
Interestingly, SNP, which exerts its vasorelaxant properties through
the generation of nitric oxide (NO), also elicited significantly less
relaxant activity in the PTHrP-overexpressing aortas (Fig. 8B).
EC50 values were 6.5 ± 1.1 and 31 ± 5
nM for wild-type and transgenic mice, respectively.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The SMP8 promoter was selected to target PTHrP to smooth muscle because
its natural gene product, smooth muscle -actin, is expressed
exclusively in smooth muscle of the adult mouse. The -1074 bp flanking
region of the mouse smooth muscle -actin promoter contains a
conserved sequence that represses expression in nonmyogenic fibroblast
cells, and a serum-response element and six E box motifs that confer
high level expression in aortic smooth muscle cells (32). The identical
segment of this promoter has recently been used to drive high level
expression of IGF-I (22) and IGF-binding protein-4 (20) to the smooth
muscle of transgenic mice. In these studies, the expression of both
IGF-I and IGF-binding protein-4 transgene constructs was entirely
confined to smooth muscle-rich tissues, precisely mimicking the pattern
of expression of the endogenous smooth muscle -actin gene. By
contrast, the SMP8-PTHrP transgene construct was expressed to variable
degrees in nonsmooth muscle tissues, particularly in adult heart and
bone, which do not express smooth muscle -actin. However, smooth
muscle -actin is transiently expressed in skeletal and cardiac
muscle during embryogenesis (33, 34). It is possible that increased
PTHrP in these tissues during embryogenesis may have delayed the
developmental program of cardiomyocytes and bone marrow stromal cells,
leading to persistence of an embryonic pattern of smooth muscle
-actin in adult tissues.
It is noteworthy that the skeletal phenotype observed in two separate
SMP8-PTHrP lines is similar to that previously described in transgenic
mice overexpressing PTHrP in growth plate chondrocytes (35). The Col
II-PTHrP mice demonstrated a hypercellular fibrous marrow immediately
adjacent to primary spongiosa reminiscent of osteitis fibrosa. As
smooth muscle -actin is known to be expressed in a subpopulation of
bone marrow stromal cells (36), its local production would be expected
to greatly accelerate bone turnover and give rise to a bone phenotype
resembling osteitis fibrosa. Unfortunately, these mice did not
reproduce, and they could not be characterized in more detail.
Nonetheless, the histopathological abnormalities evident in heart and
bone of these lines of SMP8-PTHrP transgenic mice are probably directly
attributable to the local effects of PTHrP. In addition, the relatively
low number of viable PTHrP-overexpressing mice obtained suggests that
massive overexpression during embryogenesis may have important
deleterious effects on development (28).
Transgenic mice from line 375 developed with no apparent physical abnormality and expressed the SMP8-PTHrP transgene predominantly in smooth muscle, as revealed by in situ hybridization. Measurements of cardiovascular function and characterization of vascular contractile properties in these mice provide the first in vivo evidence for a local vasorelaxant role for PTHrP. PTHrP-overexpressing mice demonstrated a significantly reduced systemic blood pressure compared with wild-type mice. This is remarkable considering the multiple compensatory mechanisms that would be expected to be triggered to maintain cardiovascular homeostasis. We recognize, however, that alterations in blood pressure in the transgenic mice occurred as the result of enforced overexpression of PTHrP and, by definition, probably represent an amplification of the physiological effects of PTHrP in the vasculature. However, the conclusion that the reduction in blood pressure is due to the overexpression of PTHrP is further strengthened by the fact that targeted overexpression of the PTH/PTHrP receptor to the smooth muscle of transgenic mice also results in animals with lowered blood pressure (28). Finally, as low levels of SMP8-PTHrP were also expressed in the brain, we cannot rule out the possibility that a component of the hypotension occurred as the result of a central effect of PTHrP.
PTHrP-overexpressing mice displayed decreased sensitivity to the effects of exogenous PTHrP on blood pressure and total peripheral resistance in vivo as well on vasorelaxation responses in organ bath preparations of aorta and portal vein. This finding is compatible with desensitization of PTH/PTHrP receptor/effector coupling mechanisms by high level expression of PTHrP within the vessel wall, as has been previously demonstrated in cultured bone and vascular smooth muscle cells (14) and murine aorta preparations (31). Although we did not attempt to directly measure receptor abundance in the transgenic mouse vasculature, Northern blot analysis of aorta, bladder, and other smooth muscle-rich tissues from these mice showed no significant changes in PTH/PTHrP receptor mRNA abundance (not shown). In addition, PTHrP-overexpressing aortas were less responsive to acetylcholine and SNP, which indicates that the mechanisms involved in the desensitization process include signaling pathways distal to the PTH/PTHrP receptor. Acetylcholine relaxes mouse aorta through endothelium-dependent NO formation, whereas SNP directly stimulates NO production in vascular smooth muscle. The mechanisms responsible for PTHrP-induced vasorelaxation remain incompletely characterized, but in the aorta they clearly depend on the presence of an intact endothelium (31). Therefore, the fact that overexpression of PTHrP desensitizes mouse vessels to the effects of both acetylcholine and SNP indicates that the signal transduction cascades of PTHrP and NO-mediated vasorelaxants converge on a common distal effector pathway.
In summary, we have selectively expressed PTHrP in smooth muscle of transgenic mice, representing the first example of successful targeting of a vasoactive agent in this tissue. When overexpressed in its normal paracrine setting, PTHrP reduces systemic blood pressure and desensitizes the vessels to further effects of exogenous PTHrP, acetylcholine, and possibly other vasorelaxants that act via a NO pathway. This transgenic mouse model should prove useful to further explore the functions of locally produced PTHrP in the cardiovascular system as well as in other smooth muscle-rich tissues such as bladder, stomach, and intestine.
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Acknowledgments |
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Footnotes |
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Received August 17, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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actin-IFGBP-4 fusion gene induces smooth muscle hypoplasia.
Endocrinology 139:2605–2614-actin gene. J Biol Chem 267:11995–12003-Smooth muscle actin is transiently expressed in embryonic rat
cardiac and skeletal muscles. Differentiation 39:161–166
-sarcomeric actin, -smooth muscle
actin and desmin during myogenesis in rat and mouse embryos. I.
Skeletal muscle. Differentiation 44:132–142[CrossRef][Medline]
-smooth muscle actin in murine bone marrow
stromal cells. Blood 78:304–309This article has been cited by other articles:
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J. Qian, M. C. Colbert, D. Witte, C.-Y. Kuan, E. Gruenstein, H. Osinska, B. Lanske, H. M. Kronenberg, and T. L. Clemens Midgestational Lethality in Mice Lacking the Parathyroid Hormone (PTH)/PTH-Related Peptide Receptor Is Associated with Abrupt Cardiomyocyte Death Endocrinology, March 1, 2003; 144(3): 1053 - 1061. [Abstract] [Full Text] [PDF]
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 K. Nobe, Y. Sakai, H. Nobe, J. Takashima, R. J. Paul, and K. Momose Enhancement Effect under High-Glucose Conditions on U46619-Induced Spontaneous Phasic Contraction in Mouse Portal Vein J. Pharmacol. Exp. Ther., March 1, 2003; 304(3): 1129 - 1142. [Abstract] [Full Text] [PDF]
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 K. Schorr, G. Taimor, H. Degenhardt, K. Weber, and K.-D. Schluter Parathyroid Hormone-Related Peptide Is Induced by Stimulation of alpha 1A-Adrenoceptors and Improves Resistance against Apoptosis in Coronary Endothelial Cells Mol. Pharmacol., January 1, 2003; 63(1): 111 - 118. [Abstract] [Full Text] [PDF]
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A. Eichinger, N. Fiaschi-Taesch, T. Massfelder, S. Fritsch, M. Barthelmebs, and J.-J. Helwig Transcript Expression of the Tuberoinfundibular Peptide (TIP)39/PTH2 Receptor System and Non-PTH1 Receptor-Mediated Tonic Effects of TIP39 and Other PTH2 Receptor Ligands in Renal Vessels Endocrinology, August 1, 2002; 143(8): 3036 - 3043. [Abstract] [Full Text] [PDF]
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T. Massfelder, N. Taesch, S. Fritsch, A. Eichinger, M. Barthelmebs, A. F. Stewart, and J.-J. Helwig Type 1 Parathyroid Hormone Receptor Expression Level Modulates Renal Tone and Plasma Renin Activity in Spontaneously Hypertensive Rat J. Am. Soc. Nephrol., March 1, 2002; 13(3): 639 - 648. |
, P < 0.05 compared
with the wild-type response.
) and
wild-type (•) mice. Individual endothelium-intact mouse aortas were
isometrically mounted and contracted with 300 nM PE. PTHrP
was administered to generate relaxation relationships. Each data
point represents the percent relaxation (mean ±
SEM) observed in six individual aortas.
