In-vivo activation of circulating inactive renin by the ischemic kidney in man

The role of the kidney as a possible source or as activator of inactive renin was studied in 22 patients with Essential Hypertension (EH) and in 20 patients with Unilateral Renal Artery Stenosis (RAS). Active and inactive renin (trypsin activation) were measured in blood samples taken simultaneously from both renal veins and from a peripheral artery during acute diuretic stimulation induced by furosemide 40 mg i.v. In EH pts active and trypsin-activated renin were significantly higher in both renal veins than in arterial blood (P less than 0.001 and P less than 0.02 respectively) whereas no difference was seen as far as inactive renin is concerned. In unilateral RAS trypsin-activated and active renin from the ischemic kidney were significantly higher (P less than 0.01 and P less than 0.005 respectively) while inactive renin was significantly lower (P less than 0.005) than in arterial blood. No significant difference was seen between arterial and renal venous blood from the contralateral kidney as far as active and inactive renin are concerned. When comparing the V-A differences for active renin to the corresponding V-A differences for inactive renin from the ischemic kidney a significant negative correlation appeared (r = -0.49 p less than 0.05) whereas no correlation was found from the contralateral kidney (r = -0.26 n.s.). These data demonstrate that the ischemic kidney, in addition to its ability to release active renin, can also activate circulating inactive renin.