MEASUREMENT OF RENIN AND SUBSTRATE CONCENTRATIONS IN HUMAN-SERUM

Methods for the measurement of renin and renin substrate by radioimmunoassay have been described. One method of measuring renin is based on the zero-order reaction velocity of angiotensin I formation when serum is incubated with an excess of hog substrate. This method was compared with a bioassay which has been described previously (A. B. Gould, L. T. Skeggs, and J. R. Kahn, 1966, Lab. Invest. 15, 1802-1813) and with another radioimmunoassay which determines renin concentration from the rate of angiotensin I formation with endogenous substrate by using the integrated form of the Michaelis-Menten equation and the kinetic constants. Similar results were obtained by these three methods when 30 samples of serum from 15 normotensive people were assayed. No evidence was found to suggest any interference by activators or inhibitors in human serum. The mean recovery of human renin added to serum in 27 experiments was 93.5 ± 10.7% (SD). In addition, the kinetic analysis of human serum showed no difference in the rate of angiotensin formation, at comparable substrate levels, in sera from normotensive people (including women taking oral contraceptives) and patients with essential hypertension. © 1979.