No Role for Prostaglandins and Bradykinin in the Autoregulation of Renal Blood Flow

In order to evaluate the participation of prostaglandins and bradykinin in autoregulation of renal blood flow, the pressure-flow relationships were examined before and during the infusion of prostaglandin E2, sodium arachidonate or bradykinin in the pump-perfused kidney of anesthetized dogs. Renal arterial pressure was changed in a step-wise fashion between 60 and 200 mmHg by means of a pneumatic resistance. Renal blood flow revealed an effective autoregulation against the pressure changes between 100 and 200 mmHg. Infusion of prostaglandin E2 (30 and 100 ng/min), sodium arachidonate (200 and 500 micrograms/min) or bradykinin (100 and 300 ng/min) into the renal artery increased renal blood flow dose-dependently, but had no influence on the autoregulation of renal blood flow. We also examined the effect of endogenous bradykinin and prostaglandins by the intravenous administration of captopril (1 mg/kg), a kininase II inhibitor, and indomethacin (2.5 mg/kg), a cyclo-oxygenase inhibitor, respectively. Captopril increased renal blood flow, but did not impair the autoregulation. Indomethacin decreased renal blood flow and had no effect on the renal autoregulation. It is considered that prostaglandins and bradykinin which induced renal vasodilation have no role in the autoregulation of renal blood flow in the dog kidney.