Disappearance of bradykinin in the renal circulation of dogs. Effects of kininase inhibition.

In chloralose-anesthetized dogs, we investigated the disappearance of bradykinin on passage across the renal circulation. The peptide was infused into a renal artery at various doses (5-200 ng/kg min-1); renal blood flow and the concentration of kinins in renal venous blood were then determined and the percent survival of bradykinin on passage through the kidney calculated. Bradykinin caused a dose-related increase in renal blood flow, urine flow, sodium excretion, and kinin content of renal venous blood. Intravenous administration of BPP9alpha (300 mug/kg), a peptide kininase II inhibitor, potentiated the renal vasodilator, diuretic, and natriuretic actions of bradykinin and augmented the survival of the kinin on passage through the kidney from 12.72 +/- 1.64% in control dogs to 53.92 +/- 7.48% (P less than 0.001). Furthermore, the values of peptide survival were positively correlated with the increases in renal blood flow (r = 0.92, P less than 0.01), urine flow (r = 0.75, P less than 0.01), and sodium excretion (r = 0.68, P less than 0.01) produced by bradykinin. In addition, BPP9alpha by itself increased renal blood flow (16%, P less than 0.01), urine flow (115%, P less than 0.005), and sodium excretion (167%, P less than 0.02). Similarly, the concentration of kinin in renal venous blood and the excretion of urinary kinins rose from 0.11 +/- 0.03 ng/ml and 4.1 +/- 1.1 ng/min to 0.24 +/- 0.05 ng/ml (P less than 0.005) and 38.5 +/- 12.2 ng/min (P less than 0.02). These studies suggest that kinins generated intrarenally play a role in the regulation of renal blood flow and salt-water excretion and that variations in the capacity of the kidney to inactivate kinins may be a determinant of the intrarenal activity of the kallikrein-kinin system.