Protracted effect of converting-enzyme inhibition on the rat's response to intraarterial bradykinin.

Intravenous infusion of the converting-enzyme (CE) inhibitor, MK422 (1 mg X kg-1 X hr-1 for 30 minutes) in normotensive controls and two-kidney, one clip (2K1C) rats in the acute phase of renovascular hypertension had a significant hypotensive effect that persisted after 24 hours. In contrast to that prolonged effect, inhibition of the pressor responses to intraarterial or intravenous angiotensin I, and the potentiation of the depressor responses to intravenous bradykinin (BK), were evident during the hour following the infusion of MK422, but not 24 hours later. Potentiation of intraarterially administered BK, however, persisted for 24 hours after infusion of the CE inhibitor. It is concluded that at least the prolonged (24-hour) effect of the treatment with MK422 was due to inhibition of the CE activity in tissues other than the lung, and that increased levels of endogenous BK may be responsible for the inhibitor's hypotensive effect.