Different effects of captopril on blood pressure in the acute and chronic two-kidney Goldblatt hypertensive dogs.

Abstract

Captopril was administered to acute (8 to 14 days after unilateral renal artery constriction) and chronic (71 to 127 days after the constriction) two-kidney Goldblatt hypertensive dogs, and to normotensive ones for 21 days (oral administration of 10, 20 and 40 mg/kg/day, consecutively each 7-day period). The decrease of arterial blood pressure was remarkable in hypertensive animals with high plasma renin activity, but not in the normotensive animals. In the acute stage of hypertension, the antihypertensive effect of captopril was dose-dependent and persistent even after its cessation. In the chronic stage of hypertension, blood pressure also decreased, but the response was not dose-dependent and did not continue after cessation. Plasma renin activity rose in both hypertensive and normotensive animals during the treatment with captopril. There were no significant changes in heart rate, daily urinary volume, sodium balance, and renal clearances of sodium (CNa), potassium (CK), chloride (CCl) and creatinine (CCr). Circulating blood volume was also not altered. These results indicate that the main mechanism of antihypertensive effect of captopril in two-kidney Goldblatt hypertensive dogs is an inhibition of the angiotensin converting enzyme. In addition, the different effects in the acute and chronic hypertensive dogs suggest that some differences exist in the mechanism(s) of maintaining blood pressure between the two stages of two-kidney Goldblatt hypertension in dogs.