Effect of captopril, a converting enzyme inhibitor on renal vascular resistance in pentobarbital anesthetized dogs.

The effects of captopril administered intravenously in a dose of 1 mg/kg on systemic blood pressure (SBP), renal blood flow (RBF) and renal vascular resistance (RVR) were examined in pentobarbital anesthetized dogs. Untreated dogs were used in experiments in which the renal artery remained intact and others in which the renal artery was partially occluded (RAO). Captopril significantly decreased SBP, increased RBF and decreased RVR in untreated dogs. RAO induced an increase in arterial plasma renin activity and this increase was accompanied by an increase in RVR in the contralateral kidney and rise in SBP. During RAO, captopril induced qualitatively similar, but greater decreases in SBP and RVR of the contralateral kidney compared with those in the untreated dogs. These results suggest the vasodilator effect of captopril depends on the background level of angiotensin II and the enhanced effect would be expected under conditions such as RAO where circulating angiotensin II contributes to vascular tone.