Plasma Renin Concentration Measured by Use of Radioimmunoassay for Angiotensin I

A method for determination of plasma renin concentration is described in which efficient inactivation of angiotensinases, use of human renin as internal standard, and radioimmunological quantitation of angiotensin I are combined. The mean recovery of angiotensin I through incubation and extraction was 84%, SD 1.3 %. In normal subjects, the plasma renin concentration was, on an average, 24 μGU/ml, range 6–59. The coefficient of variation for plasma renin determinations was 12–15%. This includes variations due to storage or dilution of plasma. The method is well-suited for routine clinical use.