Effect of chronic estradiol administration on the acute pressor response to aortic coarctation in conscious rats.
We investigated the effect of chronic estradiol administration on the pressor response elicited by acute (45 min) partial aortic constriction in conscious Wistar rats and on vascular reactivity to angiotensin II and vasopressin in vitro. Estradiol (10 micrograms kg-1 day-1, sc) or vehicle was administered for 7 days to young castrated male and female rats and to female rats that had stopped cycling (14-16 months of age). In the acute experiment of aortic coarctation in conscious rats, carotid pressure was monitored continuously before and for 45 min after partial abdominal aortic coarctation. In ovariectomized females the mean carotid pressure and heart rate before aortic coarctation were significantly lower in estradiol-treated animals (107 +/- 3 vs 119 +/- 3 mmHg and 360 +/- 31 vs 494 +/- 12 bpm). Estradiol did not affect the pressor response (145-150 mmHg) to aortic coarctation of castrated male rats or ovariectomized female rats but blunted the reflex bradycardia of ovariectomized rats. The onset of the pressor response to aortic coarctation was delayed in aged female rats as compared to the other groups. While estradiol treatment significantly accelerated the onset of hypertension in aged rats, it did not affect the pressor response of castrated animals. Full dose-response curves to angiotensin II and vasopressin were constructed in vitro in the isolated mesenteric arterial bed obtained from similarly treated groups. Estradiol did not affect the vasopressin sensitivity or responsiveness of any group, but caused a significant increase in angiotensin II sensitivity in ovariectomized rats only.(ABSTRACT TRUNCATED AT 250 WORDS)
Salgado
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MC
Departamentos de Farmacologia e Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brasil.
Castania
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JA
Ballejo
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Salgado
H C
HC
D000704:Analysis of Variance; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001017:Aortic Coarctation / Q000503:physiopathology*; D002339:Carotid Arteries / Q000187:drug effects* / Q000502:physiology; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014667:Vasopressins / Q000494:pharmacology; D014690:Venous Pressure / Q000187:drug effects*
D014667:Vasopressins; D000804:Angiotensin II; D004958:Estradiol