Renin, renin substrate and angiotensin II concentration in renal venous blood

In 22 hypertensive patients with unilateral renal artery stenosis (RAS) and in 8 patients with unilateral or bilateral renal or renal arterial disease, plasma renin activity (PRA), renin substrate (PRS), and angiotensin II (AT II) concentrations were measured in both renal veins and in a peripheral vein 1-2 h after stimulation of renin secretion by injection of frusemide. In patients with elevated PRA in venous blood from a kidney with RAS, AT II was either also elevated, lower than or equal to PRA in peripheral blood, while the contralateral kidney almost invariably extracted AT II. In the 8 patients with variable renal diseases, the concordance between PRA and AT II measurements was better. Results suggest that AT II measurements in renal venous blood are less useful in assessing the functional significance of a RAS than those of PRA. Since PRS is not different in venous plasma of the diseased and the normal kidney, PRA measurements can be regarded as proportional to plasma renin concentration in this condition.