title: Effect of in vitro administration of captopril on vascular reactivity of rat aorta.
abstract: The effect of acute administration of captopril, an angiotensin converting enzyme inhibitor, on vascular responses of rings of rat aortic smooth muscle was tested in vitro. Dose-response curves for various vasoactive agents were obtained before and after exposure to captopril (2 x 10(-4) M) for 30 minutes. In the presence of captopril, contractile responses to angiotensin I (5 x 10(-10) to 5 x 10(-8) M) were attenuated significantly, probably as a result of decreased local conversion of angiotensin I to angiotensin II. Contractile responses to angiotensin II (10(-11) to 5 x 10(-9) M) were not affected by captopril. All responses to norepinephrine (10(-9) to 10(-4) M) and phenylephrine (10(-8) to 10(-4) M) were attenuated significantly from control in the presence of captopril. In the presence of the alpha-adrenergic antagonist, phentolamine, captopril did not affect either the contractile responses to KCl (30 to 100 mM) or the isoproterenol-induced (10(-8) to 10(-5) M) relaxation of KCl-depolarized tissue. These results suggest that captopril decreased vascular responsiveness to alpha-adrenergic agonists but not to beta-adrenergic agonists. Low concentrations of bradykinin (10(-10) to 10(-8) M) induced contraction in KCl-depolarized tissue while higher concentrations (10(-7) and 10(-6) M) induced relaxation. In the presence of captopril, relaxation occurred at all concentrations of bradykinin (10(-10) to 10(-6) M), probably as a result of decreased degradation of the bradykinin. These data suggest depression of alpha-adrenergic responsiveness in vascular smooth muscle as another potential antihypertensive action of captopril.
mesh_terms: D000803:Angiotensin I / Q000037:antagonists & inhibitors; D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001920:Bradykinin / Q000037:antagonists & inhibitors; D002216:Captopril / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D011189:Potassium Chloride / Q000037:antagonists & inhibitors; D011392:Proline / Q000031:analogs & derivatives*; D051381:Rats; D011919:Rats, Inbred Strains; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D000804:Angiotensin II; D010656:Phenylephrine; D011189:Potassium Chloride; D000803:Angiotensin I; D011392:Proline; D002216:Captopril; D007545:Isoproterenol; D001920:Bradykinin; D009638:Norepinephrine