A simple radioimmunological method for the determination or renal renin activity in the rat.

A RIA method for the measurement of RRA is described, based upon the incubation of two dilutions of kidney extract with a fixed amount of EDTA-anticoagulated anephric rat plasma. The RIA of the generated angiotensin I is carried out with the commercially available NEN Kit. Recovery of angiotensin I added to the incubation mixture was 98 percent. There were 113 kidneys with a wide range of renin activity (52 to 1,274 ng. angiotensinl/mg. of kidney per hour) assayed. The within-assay coefficient of variation was uniform throughout the range, equalling 4.4 percent. The between-assay variance was practically identical with the within-assay variance. The confidence interval to the mean RRA level of one pair of readings was 5.4 percent of this mean.