Role of bradykinin potentiation in the antihypertensive effect of captopril in conscious rabbits with two-kidney, one-clip hypertension.

The role of bradykinin potentiation in the antihypertensive effect of captopril was assessed in conscious rabbits with two-kidney, one-clip hypertension. On the 35th day after clipping the renal artery, a bolus injection of bradykinin 0.2 microgram/kg was repeated at 15-min intervals three times before and for 180 min after the administration of captopril 0.5 mg/kg. The magnitude and duration of captopril-induced hypotension were more marked in hypertensive rabbits than in controls. The bradykinin-induced hypotension was markedly enhanced by captopril. However, the bradykinin potentiation by captopril was not correlated with its vasodepressive effect. On the other hand, a close relationship (r = 0.825, p less than 0.001) was observed between plasma renin activity and the maximum reduction in blood pressure induced by captopril. The experiment performed after sodium depletion for 7 days revealed that the bradykinin potentiating effect of captopril was not affected by sodium depletion. Therefore, it is concluded that the vasodepression by captopril does not necessarily depend on its bradykinin potentiating action and the latter is not influenced by the renin-angiotensin system or fluid volume depletion.