Effect of chronic treatment with captopril on reactivity of aortic smooth muscle from normotensive and renal hypertensive rats.
Acute administration of the angiotensin I converting enzyme inhibitor, captopril (2 X 10(-4) M), was shown in an earlier study to attenuate the contractile responses of aortic rings of rats to alpha-adrenergic agonists in vitro. The objective of the present study was to determine the effect of chronic treatment with captopril on reactivity of aortic rings from both normotensive and renal hypertensive rats when captopril was no longer present. Four groups of rats were used: (1) normotensive, untreated; (2) normotensive, captopril-treated (48 mg/kg b.w. per day for five weeks); (3) hypertensive (bilateral renal encapsulation for five weeks), untreated and (4) hypertensive, captopril-treated. Renal encapsulation was associated with a significant increase in systolic blood pressure, which was prevented by concomitant treatment with captopril. At the end of the five weeks treatment aortic rings, 4 mm in length, were washed for 2 h to remove the captopril, following which contractile responses to various vasoactive agents were studied in vitro. Chronic treatment with captopril attenuated significantly contractile responses to both norepinephrine (10(-9) to 10(-5) M) and phenylephrine (10(-8) to 10(-4) M) but had no effect on isoproterenol-induced relaxation of KCl-depolarized tissue in the presence of 10(-5) M phentolamine. Contractile responses to angiotension I (10(-10) to 10(-7) M) did not differ statistically among the four groups. Following addition of captopril (2 X 10(-4) m) to the bath for 30 min, contractile responses to angiotensin I were attenuated in all four groups of rings.(ABSTRACT TRUNCATED AT 250 WORDS)
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000803:Angiotensin I / Q000037:antagonists & inhibitors; D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology*; D005260:Female; D006977:Hypertension, Renal / Q000503:physiopathology*; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D009929:Organ Size / Q000187:drug effects; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D011189:Potassium Chloride / Q000037:antagonists & inhibitors; D011392:Proline / Q000031:analogs & derivatives*; D051381:Rats; D011919:Rats, Inbred Strains
D000316:Adrenergic alpha-Agonists; D000804:Angiotensin II; D010656:Phenylephrine; D011189:Potassium Chloride; D000803:Angiotensin I; D011392:Proline; D002216:Captopril; D007545:Isoproterenol; D009638:Norepinephrine