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1 Service de Pharmacologie
Clinique, Vascular endothelial growth factor (VEGF) is
an endothelial cell-specific mitogen that is upregulated during
exposure to hypoxia. In this study, we analyzed heart and lung VEGF
mRNA expression and examined pulmonary vascular remodeling as well as
myocardial capillary density in two rat models of pulmonary
hypertension involving exposure to chronic hypoxia (CH) and treatment
with monocrotaline (MCT), respectively. The rats were studied after 0.5, 1, 3, 15, and 30 days of exposure to 10%
O2 or 1, 6, and 30 days after a
subcutaneous MCT injection (60 mg/kg). Both CH and MCT induced
pulmonary hypertension and hypertrophy of the right ventricle (RV) with
increased RV weight and atrial natriuretic peptide mRNA expression.
VEGF mRNA expression as assessed by Northern blot analysis was potently
induced after 12 h of hypoxia in both the right and left ventricles.
After prolonged exposure to hypoxia, VEGF mRNA returned to baseline in
the left ventricle (LV) but remained increased in the RV, where it
peaked after 30 days. In MCT rats, VEGF mRNA was unchanged in the LV
but decreased by 50% in the RV and by 90% in the lungs after 30 days.
VEGF mRNA remained unchanged in the lungs from CH rats. Pulmonary
vascular remodeling was more pronounced in MCT than in CH rats. The
number of capillaries per RV myocyte was increased in rats exposed to
30 days of hypoxia, whereas it remained unchanged in MCT rats despite a
similar degree of RV hypertrophy. Our results suggest that the
sustained increase in VEGF expression in the hypertrophied RV during CH
may account for the increased number of capillaries per myocyte. In
contrast, reduced VEGF expression in the lungs and RV of MCT rats may
aggravate pulmonary vascular remodeling and compromise RV myocardial perfusion.
vascular endothelial growth factor; pulmonary hypertension; hypoxia; monocrotaline; right ventricular hypertrophy
VASCULAR ENDOTHELIAL GROWTH FACTOR (VEGF) was first
described as a potent and specific mitogen for endothelial cells (8) and a vascular permeability factor (12). It was then found to play an
important role in normal as well as pathological angiogenesis (26). A
unique feature of VEGF is its sensitivity to hypoxia. Hypoxia is a
strong inducer of VEGF expression in vitro (11, 19, 29). The mechanism
of hypoxic induction of VEGF expression has been partially elucidated.
Hypoxia activates a specific transcription factor (hypoxia-inducible
factor) that binds to identified hypoxia-sensitive elements in the
promoter of the VEGF gene (9). Hypoxia may also increase VEGF
expression by stabilizing VEGF mRNAs (13, 30).
Regulation of VEGF expression in tissues is less well documented. In
the heart, VEGF is mainly expressed by myocytes. Increased expression
of cardiac VEGF has been documented in several models of acute and
chronic ischemia (4, 10, 15). Whether this VEGF increase
contributes to ischemic angiogenesis is not known. In the lung, VEGF is
primarily expressed by epithelial cells, which are in close proximity
to endothelial cells (21) and may play a role in the regulation of
endothelial cell turnover, differentiation, and vascular permeability.
Increased VEGF expression has been reported in the lungs of rats
exposed to chronic hypoxia (CH) (31) and may play a role in the
vascular remodeling associated with the development of pulmonary hypertension.
In this study, we examined the effects of exposure to CH and treatment
with monocrotaline (MCT) on VEGF gene expression in heart and lung
tissues of rats. Both CH and MCT induce pulmonary hypertension and
remodeling of pulmonary vessels with medial thickening of muscularized
arteries and appearance of smooth muscle cells in normally
nonmuscularized distal arteries (18, 27). Because pulmonary
hypertension is also associated with right ventricular (RV) hypertrophy
and, potentially, with alterations in myocardial angiogenic processes,
we also sought to determine whether alterations in VEGF mRNA expression
in the RV were associated with changes in coronary capillary density in
the same groups of rats.
Study Design
ABSTRACT
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
INTRODUCTION
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
Chronic Hypoxia
Group 1 rats were exposed to CH (10% O2) in a ventilated chamber (500-liter volume; Flufrance, Cachan, France), as previously described (1). To establish a hypoxic environment, the chamber was flushed with a mixture of room air and N2, and the gas was then recirculated. Chamber environment was monitored using an O2 analyzer (model OA150, Servomex, Crowborough, UK). CO2 was removed by using soda lime granules, and excess humidity was prevented by cooling of the recirculation circuit. Temperature in the chamber was 22-24°C. The chamber was opened on alternate days for 1 h for cleaning of the cages and replenishing of food and water supplies.MCT Treatment
MCT (Sigma Chemical) was dissolved in PBS and the pH adjusted to 7.4 with 0.5 N HCl. The MCT solution was given as a single subcutaneous injection (60 mg/kg). Control rats were injected with the same volume of saline. Mortality was high in MCT-treated rats compared with that in rats exposed to CH (33% in MCT group vs. 0% in CH group).Hemodynamic Measurements and Assessment of RV Hypertrophy
Hemodynamic measurements were performed 30 days after the experiments were started. Rats were anesthetized using an intramuscular injection of ketamine (20 mg/100 g) and xylazine (1 mg/100 g). After exposure of the right jugular vein, a polyvinyl catheter was inserted and manipulated through the RV into the pulmonary artery. A polyethylene catheter was inserted into the right carotid artery. Pulmonary and systemic arterial pressures were measured immediately after insertion of the catheters using Gould P23 ID transducers coupled to pressure modules and a Gould TA 550 multichannel recorder. Only pulmonary artery pressures successfully recorded within 30 min of catheter insertion were taken into account.Finally, after an intraperitoneal injection of pentobarbital sodium (20 mg/kg), the thorax was opened. In some experiments, the heart was
arrested in diastole by injection of KCl, quickly removed, and frozen
at 
80°C for a structural study at a later date. In other
experiments, the heart was excised and weighed, and the ratio of RV
free wall to septum plus left ventricular (LV) free wall weight was
estimated. The lungs were prepared for a structural study.
Structural Studies
Heart.
Cross sections (10 µm thick) were cut using a cryostat, thawed on
Super Frost/Plus (Menzel-Glaser) slides, and stored in black, sealed
boxes at 20°C until used. Number and mean cross-sectional diameter of myocytes were measured on sections stained by
hematoxylin-phloxin-saffron.
Lung. Arteries from isolated lungs were injected with a minimum sulfate-gelatin mixture at 50°C with a perfusion pressure of 75 mmHg through a cannula placed in the main pulmonary artery. Pressure was maintained for 5 min, the time necessary to cause subpleural filling of normal lungs. The lungs were fixed in the distended state by infusion of 4% aqueous buffered Formalin into the trachea at a pressure of 25 cmH2O. The entire specimen was left in a bath of the same fixative for 1 wk. A midsagittal slice of the right lung including the apical, azygous, and diaphragmatic lobes was processed for paraffin embedding. Sections 5 µm thick were cut for light microscopy and stained with hematoxylin-phloxin-saffron and orcein-picroindigo-carmine. In each rat, a total of 35-65 intra-acinar vessels were analyzed to assess the distribution and the degree of muscularization according to the accompanying airway, i.e., an alveolar duct or alveolus. Intra-acinar vessels were categorized as muscular, partially muscular, and nonmuscular. Muscularization was defined as the presence of typical cells stained red by phloxin, exhibiting an elongated shape and square-ended nuclei, and bound by two orcein-stained elastic laminae. The external diameter (distance between and including the two external elastic laminae intersected by the diameter) and medial thickness (distance from the luminal surface of the internal elastic laminae to the abluminal surface of the external laminae) were recorded for all muscular and partially muscular arteries. Normalized wall thickness (WTN) was calculated using the following formula
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Northern Blot Experiments
Measurements of VEGF mRNA levels were performed in heart and lung tissues from rats not previously subjected to hemodynamic studies. Total RNA was isolated from the tissues using the method of Chomczynski and Sacchi (7) and was quantitated spectrophotometrically at 260 nm. Ten micrograms of total RNA were subjected to denaturing electrophoresis on 1.2% agarose formaldehyde gels and transferred to Hybond-N membranes (Amersham) before hybridization with selected probes. Complementary DNA probes including rat VEGF and 18S rRNA (both provided by Dr. A. Ladoux) were 32P labeled using the multiprime DNA labeling system (Promega). An atrial natriuretic peptide (ANP) antisense oligonucleotide (a gift from Dr. J. J. Mercadier, Paris, France) was labeled by tailing with a DNA 3'-end labeling kit (Boehringer Mannheim). Specific activities were >5 × 108 counts per minute per gram of DNA. Hybridizations with VEGF and 18S rRNA were performed under low-stringency conditions [30% formamide, 5× SSPE (1× SSPE is 0.15 M NaCl, 0.01 M Na2HPO4, and 0.001 M EDTA, pH 7.4), 5× Denhardt's solution, 0.1% SDS, and 100 mg/ml salmon sperm DNA] at 43°C. Hybridization with ANP antisense oligonucleotides was performed using 50% formamide, 5× SSPE, 5× Denhardt's solution, 0.1% SDS, and 100 mg/ml salmon sperm DNA at 46°C. After overnight hybridization, blots were washed twice in 2× SSPE and 0.1% SDS for 15 min and then twice in 1× SSPE and 0.1% SDS for 15 min. Relative amounts of radiolabeled cDNA that hybridized to the blots were quantitated by phosphorimaging and scanning densitometry and were normalized to 18S rRNA levels to control for loading errors. All enzymes were from Promega. All radioactive materials were from Amersham and ICN.Reverse Transcription-Polymerase Chain Reaction
Reverse transcription-polymerase chain reaction (RT-PCR) was performed to identify the different VEGF isoforms in heart and lung tissues (11). The primers used were 5'-CCATGAACTTTCTGCTCTCTTG-3' (sense) and 5'-GGTGAGAGGTCTAGTTCCCGA-3' (antisense). Conditions were 3 min of denaturation at 94°C, followed by 35 cycles consisting of 45 s at 92°C, 1 min at 54°C, and 90 s at 72°C. Samples were then treated at 72°C for 10 min. The PCR products were analyzed by agarose gel electrophoresis.Statistical Analysis
The data are expressed as means ± SE. Unpaired Student's t-tests were used for single comparisons of VEGF and ANP mRNA levels in the CH and MCT groups with their respective controls. Multiple comparisons between groups were performed using the Kruskal-Wallis test, followed when significant by Dunn's test. P values of
0.05 were
considered statistically significant.
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RESULTS |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Effects of CH or MCT on Heart Weight and Hemodynamics
Final body weight was significantly lower in MCT-treated rats than in the other two groups 30 days after the experiments were started (P < 0.05; Table 1). Compared with rats treated with saline and exposed to room air, rats given MCT or exposed to hypoxia for 30 days exhibited significant increases in pulmonary artery pressure (P < 0.05) and in RV weight (P < 0.01), whereas LV weight did not differ among the three groups. Pulmonary arterial pressure tended to be higher in MCT than in CH rats, although the difference did not reach statistical significance. However, the degree of RV hypertrophy, as assessed on the basis of the ratio of RV to LV plus septum weight, was similar in the MCT and CH groups. Heart rate and systemic artery pressure were similar in CH rats and in controls, whereas systemic artery pressure was lower in MCT rats (P < 0.01).
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In rats studied after different durations of exposure to hypoxia, RV hypertrophy became significant after 15 days of hypoxia compared with controls, and, in MCT-treated rats, 30 days after the injection (Fig. 1).
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ANP mRNA used as a molecular marker of cardiac hypertrophy (17) was significantly increased in RV tissue after 15 and 30 days of exposure to hypoxia as well as 30 days after MCT treatment (P < 0.01; Fig. 2). Expression of ANP in LV tissue remained low in the three groups.
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VEGF mRNA Expression in Heart and Lung Tissue
VEGF mRNA expression in heart and lung tissues from CH rats was analyzed comparatively with 18S rRNA expression using Northern blots. In every case, the VEGF probe hybridized to a 3.7-kb mRNA species. As shown in Fig. 3, LV exposed to hypoxia exhibited a transient 5.5-fold increase in VEGF mRNA level, which peaked at 12 h and then returned to control levels at 24 h. In contrast, RV exposed to hypoxia showed a sustained increase in VEGF mRNA, with a peak (4.5-fold) after 30 days. No changes in lung VEGF mRNA levels were observed in CH rats.
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In MCT rats, VEGF mRNA expression was studied 1, 6, and 30 days after the injection (Fig. 4). In the RV, VEGF mRNA was decreased by 50% after 30 days. In lung tissue, VEGF mRNA decreased by 90% after 30 days; only a slight and nonsignificant decrease was noted at day 6 (30%). VEGF mRNA levels remained unaltered in the LV (data not shown).
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To identify VEGF transcript isoforms, RT-PCR experiments were performed (Fig. 5). The main transcript in both heart and lung tissues from control, MCT, and CH rats was VEGF 188.
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Structural Study of Heart
Compared with normoxia and a saline injection, MCT administration or exposure to hypoxia for 30 days caused a significant increase in myocyte cross-sectional diameter (Fig. 6). This increase was larger in MCT than in CH rats. No changes in LV myocyte diameter were observed in either group (data not shown).
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In the RV myocardium, the number of capillaries per square millimeter did not differ between CH and control rats studied after 30 days but was significantly lower in MCT-treated animals than in rats exposed to hypoxia for 30 days (P < 0.01). However, because of myocyte hypertrophy, the ratio of the number of capillaries to the number of myocytes was increased in CH rats and unchanged in MCT rats. Representative photomicrographs are presented in Fig. 7.
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Structural Study of Lung
Data are summarized in Table 2. The number of alveoli divided by the number of small arteries (50- to 200-µm diameter) did not differ among the three groups. Compared with observations in control animals, an increase in arterial wall thickness and prominent muscularization of normally nonmuscularized arteries were observed at both the alveolar duct and the alveolar wall level in lungs from MCT and CH rats. Muscularization was more marked in MCT than in CH rats.
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DISCUSSION |
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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The present results show that exposure to CH or treatment with MCT, both providing pulmonary hypertension and subsequent RV hypertrophy in rats, is associated with different changes in RV VEGF mRNA expression and RV capillary density. MCT-treated rats showed a decrease in RV VEGF mRNA and RV capillary density, whereas rats exposed to CH showed an increase in RV VEGF mRNA expression and preserved capillary density. Taken together, these findings suggest that VEGF may play an important role in controlling RV perfusion during hypertrophy secondary to pulmonary hypertension. Moreover, lung VEGF mRNA levels were also strikingly decreased in rats given MCT but remained unchanged after exposure to hypoxia. Because remodeling in distal vessels was also more marked in MCT than in hypoxic rats, it can be speculated that alterations in lung VEGF expression also play a role in the development of pulmonary hypertension.
Pulmonary hypertension is characterized by an increase in pulmonary vascular resistance that impedes ejection of blood by the RV and leads to RV hypertrophy. There is ample evidence that some forms of pathological cardiac hypertrophy, particularly those produced by pressure overload, are associated with a decrease in capillary density, which is most marked in the subendocardial layers of the hypertrophied ventricle (16, 22, 23). This reduction in capillary density may arise as a consequence of an increase in myocardial mass without parallel growth of the microvascular bed. In our study, capillary density was assessed in the subendocardial layers of the RV in two experimental models of pulmonary hypertension involving exposure to CH and treatment with MCT, respectively. We found that capillary density was not modified in the RV from hypoxic rats, whereas the myocytes were enlarged, resulting in an increase in the mean number of capillaries per myocyte suggestive of angiogenesis. In contrast, in rats studied 30 days after MCT administration, capillary density was reduced, the myocytes were greatly enlarged, and the mean number of capillaries per myocyte was unchanged. These results suggest that an angiogenic process accompanied RV hypertrophy in hypoxic but not in MCT-treated rats.
Our observation that RV hypertrophy caused by hypoxic pulmonary hypertension was associated with an increase in the number of capillaries per myocyte is consistent with data reported in other types of cardiac hypertrophy. LV hypertrophy secondary to hyperthyroidism (6) and cardiac hypertrophy occurring in utero (32) have been shown to be associated with increased coronary vascular growth. This observation is of importance when considering functional characteristics of the hypertrophied ventricle. Inadequate growth of the coronary microvascular bed is among the factors that limit myocardial perfusion in mature hearts with pressure-overload hypertrophy.
In accordance with our observation that angiogenesis occurred in the RV from hypoxic rats but not in those from MCT-treated rats, we found that the VEGF mRNA level was increased in the RV from hypoxic rats and decreased in those from MCT-treated rats. VEGF is a potent angiogenic factor (12), and upregulation of VEGF gene expression was sustained in the hypertrophied RV from CH rats, suggesting that VEGF produced in response to CH could be involved in the angiogenic process in the RV.
In response to acute hypoxia, both the RV and the LV responded with an increase in the VEGF transcript. With prolonged exposure, this increase was sustained in the RV, whereas VEGF mRNA returned to baseline within 24 h in the LV. This suggests that transient expression of the VEGF gene is probably not sufficient to induce neoangiogenesis, which may require sustained expression as observed in the RV in our study. The sustained increase in VEGF mRNA in the RV may have been related to development of selective hypertrophy of the RV. However, RV hypertrophy occurred only after 2 wk of exposure to hypoxia, whereas VEGF mRNA levels in the RV tissue were already elevated during the first 2 wk. Moreover, ANP gene expression was not elevated during the first 2 wk of exposure to hypoxia. In view of these findings, it is unlikely that the increased VEGF gene expression in the RV during hypoxia was related to the hypertrophic process per se. Furthermore, in the MCT-treated rats, which also developed RV hypertrophy, both a reduction in VEGF gene expression and an increase in ANP gene expression were seen. It is difficult to explain why the two models of pulmonary hypertension with RV hypertrophy used in our study induced opposite changes in VEGF gene expression. One possibility is that RV hypertrophy may be generally associated with a decline in VEGF gene expression, with this effect being counteracted by hypoxia. The fact that in the MCT model VEGF transcript levels declined in the RV but not in the LV lends credence to this hypothesis. However, we cannot rule out that a decrease of VEGF expression in RV was related to end-stage heart failure. Low heart rate and systemic artery pressure suggest that cardiac output was markedly decreased 30 days after MCT administration. Similar late alterations of hemodynamics have been previously reported (18). Such a development of RV failure might also have contributed to increase ANP gene expression in the MCT group.
Conflicting results have been reported regarding VEGF expression in hypoxic lungs. Tuder et al. (31) reported a 1.7-fold increase in VEGF transcript levels in lungs from rats exposed to hypoxia for 30 days. In contrast, Sandner et al. (28) found no change in lung VEGF mRNA levels in rats exposed to hypoxic conditions for 6 h. Also, Pfeifer et al. (25) did not observe any increase in VEGF mRNA in lung tissue from rats exposed to hypoxia of various duration. In our study, VEGF mRNA levels were unaltered in lungs from rats exposed to hypoxia for 12 h to 30 days. Our data suggest that VEGF gene expression in hypoxic animals may vary across tissues. In the present study, VEGF transcript levels in chronically hypoxic animals showed a sustained increase in the RV, a transient increase in the LV, and no change in the lungs. During exposure to hypoxia, PO2 levels may differ in these tissues. In the RV, as systolic pressure increases in response to hypoxia, compression of the coronary vessels becomes more marked during systole. This obstacle to myocardial perfusion in the face of an increased O2 demand may result in particularly low PO2 values in the RV myocardium. However, we cannot exclude that sensitivity to hypoxia may differ across tissues or that sustained VEGF gene expression may depend on factors other than hypoxia.
Another finding from our study is that in MCT-treated rats, development of pulmonary hypertension and RV hypertrophy were associated with decreases in VEGF mRNA levels in the lungs and RV. This decrease in VEGF gene expression was not caused by a nonselective toxic effect of MCT because VEGF mRNA levels were unaltered in the LV. Tuder et al. (31) reported a decrease in VEGF mRNA levels in lungs from endotoxin-treated rats. They also showed that inhibitors of nitric oxide (NO) synthase increased VEGF mRNA levels and suggested that NO produced by the inducible form of NO synthase may downregulate VEGF expression in endotoxin-treated rats. Treatment with MCT is known to be associated with accumulation of inflammatory cells in the intra-alveolar space and production of proinflammatory cytokines (2, 5, 20, 24, 33). Whether the decrease in VEGF mRNA levels observed in our MCT rats was caused by increased production of NO remains to be determined.
Structural alterations in the pulmonary vascular bed during pulmonary hypertension include muscularization of distal, normally nonmuscularized, arteries and medial hypertrophy of muscular arteries. Loss of distal functional pulmonary arteries has also been described in both the hypoxic and MCT models of pulmonary hypertension (18, 27). This has been shown to be caused, in part, by a gradual increase in the thickness of the vascular wall, responsible for a decrease in the luminal diameter and, finally, for occlusion of small arteries. Failure of angiogenic processes may play a role in these changes. Previous studies found reduced numbers of vessels in lungs from rats with pulmonary hypertension caused by hypoxia or MCT, with the decrease being more pronounced in the MCT model. Moreover, vessel numbers were inversely related to the severity of pulmonary hypertension. In the present study, structural remodeling was more severe in MCT-treated than in hypoxia-adapted rats. Although the number of distal vessels did not differ between the two groups of pulmonary hypertensive rats, muscularization was more marked and medial thickness greater in the vessels from MCT-treated rats. Endothelium is known to play an important role in the regulation of vascular tone and also to participate in the pathological processes of vascular remodeling. In a previous study, application of VEGF has been shown to promote reendothelialization and to attenuate neointimal thickening caused by smooth muscle cell proliferation (3). It may be speculated that, in some pulmonary hypertensive states, VEGF may help to maintain endothelial cell function such as production of antiproliferative factors and, therefore, indirectly exert protective effects against vascular remodeling.
In conclusion, stimuli that induce pulmonary hypertension and RV hypertrophy may differentially influence the functional and anatomic responses of pulmonary and coronary vessels. This may have important consequences on the severity and outcome of pulmonary hypertension. In our study, mortality was high in MCT-treated rats, whereas prolonged exposure to hypoxia was well tolerated. These results may be of clinical relevance. Failure of angiogenesis, causing RV ischemia, may play an important role in terminal decompensation and mortality of some patients with severe pulmonary hypertension.
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ACKNOWLEDGEMENTS |
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This study was supported in part by a grant from the Institut Electricité Santé.
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FOOTNOTES |
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Address for reprint requests: S. Adnot, INSERM U 492, Faculté de Médecine, 8 Rue du Général Sarrail, 94010 Créteil, France.
Received 9 December 1997; accepted in final form 7 August 1998.
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REFERENCES |
|---|
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Top
Abstract
Introduction
Materials & Methods
Results
Discussion
References
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1.
Adnot, S.,
B. Raffestin,
S. Eddahibi,
P. Braquet,
and
P. E. Chabrier.
Loss of endothelium-dependent relaxant activity in the pulmonary circulation of rats exposed to chronic hypoxia.
J. Clin. Invest.
87:
155-162,
1991.
2.
Arcot, S. S.,
D. W. Lipke,
M. N. Gillespie,
and
J. W. Olson.
Alterations of growth factor transcripts in rat lungs during development of monocrotaline-induced pulmonary hypertension.
Biochem. Pharmacol.
46:
1086-1091,
1993[Medline].
3.
Asahara, T.,
C. Bauters,
C. Pastore,
M. Kearny,
S. Rossow,
S. Bunting,
N. Ferrara,
J. Symes,
and
J. M. Isner.
Local delivery of vascular endothelial growth factor accelerates reendothelialization and attenuates intimal hyperplasia in balloon-injured rat carotid artery.
Circulation
91:
2793-2801,
1995
4.
Banai, S.,
D. Shweiki,
A. Pinson,
M. Chandra,
G. Lazarovici,
and
E. Keshet.
Upregulation of vascular endothelial growth factor expression induced by myocardial ischemia: implications for coronary angiogenesis.
Cardiovasc. Res.
28:
1176-1179,
1994
5.
Boor, P. J.,
A. I. Gotlieb,
E. C. Joseph,
W. D. Kerns,
R. A. Roth,
and
K. E. Tomaszewski.
Chemical-induced vasculature injury. Summary of the symposium presented at the 32nd annual meeting of the Society of Toxicology, New Orleans, Louisiana, March 1993.
Toxicol. Appl. Pharmacol.
132:
177-195,
1995[Medline].
6.
Chilian, W. M.,
R. D. Wangler,
K. G. Peters,
R. J. Tomanek,
and
M. L. Marcus.
Thyroxine-induced left ventricular hypertrophy in the rat. Anatomical and physiological evidence for angiogenesis.
Circ. Res.
57:
591-598,
1985
7.
Chomczynski, P.,
and
N. Sacchi.
Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction.
Anal. Biochem.
162:
156-159,
1987[Medline].
8.
Ferrara, N.,
and
W. J. Henzel.
Pituitary follicular cells secrete a novel heparin-binding growth factor specific for vascular endothelial cells.
Biochem. Biophys. Res. Commun.
161:
851-858,
1989[Medline].
9.
Forsythe, J. A., B. H. Jiang, N. V. Iyer, F. Agani, S. W. Leung, R. D. Koos, and
G. L. Semenza. Activation of vascular endothelial growth
factor gene transcription by hypoxia-inducible factor 1. Mol. Cell. Biol. 4604-4613, 1996.
10.
Hashimoto, E.,
T. Ogita,
T. Nakaoka,
R. Matsuoka,
A. Takao,
and
Y. Kira.
Rapid induction of vascular endothelial growth factor expression by transient ischemia in rat heart.
Am. J. Physiol.
267 (Heart Circ. Physiol. 36):
H1948-H1954,
1994
11.
Ladoux, A.,
and
C. Frelin.
Hypoxia is a strong inducer of vascular endothelial growth factor mRNA expression in the heart.
Biochem. Biophys. Res. Commun.
195:
1005-1010,
1993[Medline].
12.
Leung, D. W.,
G. Cachianes,
W. J. Kuang,
D. V. Goeddel,
and
N. Ferrara.
Vascular endothelial growth factor is a secreted angiogenic mitogen.
Science
246:
1306-1309,
1989
13.
Levy, A. P.,
N. S. Levy,
and
M. A. Goldberg.
Post-transcriptional regulation of vascular endothelial growth factor mRNA by hypoxia.
J. Biol. Chem.
271:
2746-2753,
1996
14.
Levy, B. I.,
J. L. Samuel,
V. E. Kotelianski,
F. Marott,
P. Poitevin,
and
R. S. Chadwick.
Morphometric measurement of subendocardial vessel dimensions in systolic and diastolic arrested rat heart.
In: Recent Advances in Coronary Circulation, edited by Y. Maruyama,
F. Kajia,
J. I. E. Hoffman,
and J. A. E. Spaan. Tokyo: Springer Verlag, 1993, p. 83-90.
15.
Li, J.,
L. F. Brown,
M. G. Hibberd,
J. D. Grossman,
J. P. Morgan,
and
M. Simons.
VEGF, flk-1, and flt-1 expression in a rat myocardial infarction model of angiogenesis.
Am. J. Physiol.
270 (Heart Circ. Physiol. 39):
H1803-H1811,
1996
16.
Marcus, M. L., D. G. Harrison, W. M. Chilian, S. Koyanagi, T. Inou, R. J. Tomanek, J. B. Martins, C. L. Eastham, and L. F. Hiratzka.
Alterations in the coronary circulation in hypertrophied
ventricles. Circulation 75, Suppl. I: I-19-I-25, 1987.
17.
Matsubara, H.,
J. Yamamoto,
Y. Hirata,
Y. Mori,
S. Oikawa,
and
M. Inada.
Changes of atrial natriuretic peptide and its messenger RNA with development and regression of cardiac hypertrophy in renovascular hypertensive rats.
Circ. Res.
66:
176-184,
1990
18.
Meyrick, B.,
W. Gamble,
and
L. Reid.
Development of Crotalaria pulmonary hypertension: hemodynamic and structural study.
Am. J. Physiol.
239 (Heart Circ. Physiol. 8):
H692-H702,
1980.
19.
Minchenko, A.,
T. Bauer,
S. Salceda,
and
J. Caro.
Hypoxic stimulation of vascular endothelial growth factor expression in vivo and in vitro.
Lab. Invest.
71:
374-379,
1994[Medline].
20.
Miyata, M.,
F. Sakuma,
A. Yoshimura,
H. Ishikawa,
T. Nishimaki,
and
R. Kasukawa.
Pulmonary hypertension in rats. 1. Role of bromodeoxyuridine-positive mononuclear cells and alveolar macrophages.
Int. Arch. Allergy Immunol.
108:
281-286,
1995[Medline].
21.
Monacci, W. T.,
M. J. Merrill,
and
E. H. Oldfield.
Expression of vascular permeability factor/vascular endothelial growth factor in normal rat tissues.
Am. J. Physiol.
264 (Cell Physiol. 33):
C995-C1002,
1993
22.
Murray, P. A.,
and
S. F. Vatner.
Reduction of maximal coronary vasodilator capacity in conscious dogs with severe right ventricular hypertrophy.
Circ. Res.
48:
27-33,
1981.
23.
Murray, P. A.,
S. F. Vatner,
and
P. B. Brigham.
Abnormal coronary vascular response to exercise in dogs with severe right ventricular hypertrophy.
J. Clin. Invest.
67:
1314-1323,
1981.
24.
Perkett, E. A.,
R. M. Lyons,
H. L. Moses,
K. L. Brigham,
and
B. Meyrick.
Transforming growth factor-
activity in sheep lung lymph during the development of pulmonary hypertension.
J. Clin. Invest.
86:
1459-1464,
1990.
25.
Pfeifer, M.,
F. C. Blumberg,
K. Wolf,
P. Sander,
D. Elsner,
G. A. J. Riegger,
and
A. Kurtz.
Vascular remodeling and growth factor gene expression in the rat lung during hypoxia.
Respir. Physiol.
111:
201-212,
1998[Medline].
26.
Plate, K. H.,
G. Breier,
H. A. Weich,
and
W. Risau.
Vascular endothelial growth is a potential tumor angiogenesis factor in vivo.
Nature
359:
845-847,
1992[Medline].
27.
Rabinovitch, M.,
W. Gamble,
A. Nadas,
O. S. Miettinen,
and
L. Reid.
Rat pulmonary circulation after chronic hypoxia: hemodynamic and structural features.
Am. J. Physiol.
236 (Heart Circ. Physiol. 5):
H818-H827,
1979
28.
Sandner, P.,
B. Gess,
K. Wolf,
and
A. Kurtz.
Divergent regulation of vascular endothelial growth factor and of erythropoietin gene expression in vivo.
Pflügers Arch.
431:
905-912,
1996[Medline].
29.
Shweiki, D.,
A. Itin,
D. Soffer,
and
E. Keshet.
Vascular endothelial growth factor induced by hypoxia may mediate hypoxia-initiated angiogenesis.
Nature
359:
843-845,
1992[Medline].
30.
Stein, I.,
M. Neeman,
D. Shweiki,
A. Itin,
and
E. Keshet.
Stabilization of vascular endothelial growth factor mRNA by hypoxia and hypoglycemia and coregulation with other ischemia-induced genes.
Mol. Cell. Biol.
15:
5363-5368,
1995[Abstract].
31.
Tuder, R. M.,
B. E. Flook,
and
N. F. Voelkel.
Increased gene expression for VEGF and the VEGF receptors KDR/Flk and Flt in lungs exposed to acute or to chronic hypoxia. Modulation of gene expression by nitric oxide.
J. Clin. Invest.
95:
1798-1807,
1995.
32.
Vlahakes, G. J., K. Turley, E. D. Verrier,
and J. I. E. Hoffman. Greater maximal coronary flow in
conscious lambs with experimental congenital right ventricular
hypertrophy (Abstract). Circulation
62, Suppl. III: III-111,
1980.
33.
Voelkel, N. F.,
R. M. Tuder,
J. Bridges,
and
W. P. Arend.
Interleukin-1 receptor antagonist treatment reduces pulmonary hypertension generated in rats by monocrotaline.
Am. J. Respir. Cell Mol. Biol.
11:
664-675,
1994[Abstract].
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