Ultramicroassay for plasma renin concentration in the rat using the antibody-trapping technique

Abstract

Using the antibody-trapping technique, picogram quantities of angiotensin-I generated during 24 hr of incubation at 37°C were stable and fully protected against peptidases. The method employs purification of angiotensin-I antisera on DEAE-cellulose and purification of renin substrate by affinity chromatography using specific antirenin antibodies in order to remove endogenous renin. The assay was performed in a single tube without a transfer step in a total volume of 30 μl at pH 6,5 with incubation for 24 hr at 37°C. With a normal rat plasma renin concentration of 5 × 10 −4 GU ml −1, the detection limit was 10 nl or a total of 5 × 10 −9 GU. In the range 20–125 nl, precision was ±10%.