A Kinetic Method for Determination of Plasma Renin Activity Using Radioassay of Angiotensin I

Abstract

A kinetic method for determination of plasma renin activity using radioimmunoassay of angiotensin I as the indicator system is presented. Angiotensin I is generated at 37 C. in plasma with the pH adjusted to 6.0 with maleic acid and ammonium maleate buffer. Chelating agents prevent the degradation of the angiotensin I product. Plasma samples from a small series of subjects on unrestricted sodium diets were analyzed with three replicate determinations. The mean values of 2.40 mμg. and 5.38 mμg. of angiotensin I per ml. per hr. were obtained after recumbency overnight and following 4 hours of activity, respectively. Run-to-run coefficient of variation was approximately 10%.