RADIOIMMUNOASSAY FOR ALDOSTERONE WITHOUT CHROMATOGRAPHY

Abstract

ABSTRACT A radioimmunoassay for the determination of plasma aldosterone has been developed suitable for the clinical laboratory. Two ml of plasma is extracted with methylene chloride and the aldosterone concentration is determined in these extracts with two different antisera obtained from rabbits immunized with an aldosterone-oxime bovine gamma globulin conjugate. In view of the high recovery of [1,2-3H] aldosterone no internal standards are needed. The coefficient of variation within a single assay was 9.0 and 10.6 % respectively. The coefficient of variation for inter-assay determinations was 13.5 and 15.0 % The validity of the method was tested by the determination of plasma aldosterone concentration in normal subjects during postural changes and salt restriction and in patients suffering from primary hyperaldosteronism. Both antisera gave almost identical values in 161 out of 170 plasma specimens. Since both antisera differed considerably in their degree of cross-reaction with various steroid hormones, the identical values obtained with the two antisera seem to provide a good indication that no cross-reaction with substances other than aldosterone had occurred in the assay systems.