Prostaglandin independence of kinin-stimulated renin release

Bradykinin can increase prostaglandin synthesis and also stimulate renin release in vitro. Because prostaglandins also stimulate renin, studies were performed to determine whether bradykinin stimulation of renin is a function of prostaglandin synthesis. Isolated glomeruli with attendant arteriolar attachments were harvested from rat kidneys and superfused. The effluent was analyzed for renin, prostaglandins E2 and I2 (6-keto-PGF1 alpha). Bradykinin (10(-5) M) increased renin by 50% with a concomitant increase in prostacyclin (PGI2) but not in prostaglandin E2 (PGE2). The cyclooxygenase inhibitor meclofenamate (1.6 X 10(-5) M) inhibited bradykinin-induced PGI2 synthesis but not the concurrent increase in renin release. Additionally, neither the phospholipase inhibitor quinacrine (10(-2) M) nor the prostacyclin synthetase inhibitor 9,11-azoprosta-5,13-dienoic acid (Azo analogue-1) (5.67 X 10(-6) M) eliminated bradykinin-induced renin release. Superfusion with calcium-free media and EDTA increased basal renin release 2.5-fold, and bradykinin stimulated a twofold increase in renin release. Neither a high (10(-2) M) media calcium nor the calcium channel blocker nifedipine (10(-6) M) eliminated bradykinin stimulation of renin. These results suggest that bradykinin stimulation of renin is at least partially independent of prostaglandin synthesis and that bradykinin must act by some prostaglandin-independent pathway to induce renin release from isolated glomeruli.