Kidney and plasma renin in human renovascular hypertension

Renin activities were determined in plasma and in single, microdissected juxtaglomerular apparatus in 19 patients with unilateral renal artery stenosis. The mean juxtaglomerular apparatus renin concentration in the stenosed kidneys was 5.5 +/- 1.2 (SEM) mug.l-1.h-1 which is about ten times that of the suppressed renin concentration in the contralateral kidneys (0.6 +/- 0.05 mug.l-1.h-1). On the affected side a positive correlation was found between intrarenal and renal venous renin concentration (r = 0.93; p less than 0.001). Both intrarenal and renal venous renin concentrations of the stenosed kindeys were positively correlated to renin secretion rates, as calculated from renin analysis in plasma from the vena cava and renal veins. No relationship could be demonstrated between intrarenal or renal venous renin concentration and the degree of blood pressure elevation or transstenotic pressure gradient. However, a positive correlation was evident between peripheral plasma renin activity and diastolic blood pressure (r = 0.88; p less than 0.001). Comparative enzyme kinetic analyses of renin from the juxtaglomerular apparatus and renal venous plasma were performed using sheep substrate. The lowest apparent Km-values of renin were found in renal venous plasma from the stenosed kidneys (198 +/- 13 mug/l) compared with the contralateral side (301 +/- 20 mug/l; p less than 0.001). Mean apparent Km-values of juxtaglomerular apparatus renin in the stenosed (270 +/- 36 mug/l) and contralateral (292 +/- 37 mug/l) kidneys did not differ. No significant differences were found between mean apparent Km-values for renin in peripheral plasma of renovascular hypertensive patients and control subjects using either homologous human or heterologous sheep renin substrate. The results suggest that, in addition to the renin concentration other factors are relevant to chronic high blood pressure in renovascular hypertension.