Effect of upright tilting on kinins as compared to renin activity in the renal venous blood from patients with essential hypertension.

The effect of tilting on the release of renal kallikrein as compared to renin was studied by the determination of kinin concentration and plasma renin activity (PRA) in the renal veins in supine position and after 15 min of 45 degrees upright tilting in 10 patients with essential hypertension. Kinin concentration decreased from 0.62 +/- 0.05 microgram/1 (mean +/- S.E.M.) in supine position to 0.51 +/- 0.05 after tilting (p less than 0.01), while PRA increased from 2.84 +/- 0.39 microgram/1/3 h tpo 4.87 +/- 0.66 (p less than 0.001). These results indicate that tilting diminishes the release of renal kallikrein. It is suggested that decreased intrarenal generation of kinins may be of importance for the reduction of diuresis and natriuresis induced by tilting.