A radioimmunoassay for the measurement of 5-androstene-3beta, 17beta-diol in plasma.

A reliable radioimmunoassay for the determination of 5-androstene-3beta, 17beta-diol in plasma is described. Antisera were obtained by immunization of rabbits with 3beta, 17beta-dihydroxy-5-androsten-16-one coupled to bovine serum albumin in position 16. The antiserum was characterized by titer, affinity, and specificity. Only dehydroepiandrosterone (24.3 percent) and pregnenolone (2.7 percent) showed a small cross-reactivity. The assay method consisted of extraction with ether, thin-layer chromatography and endpoint determination. The reliability of the method was studied. The interassay variability was 7.5 percent at a concentration of 1.22 microgram/l. The limit of detection was 0.068 microgram/l. Specificity was achieved by chromatographic separation of the crossreacting steroids. Mass recovery experiments with 250 and 500 pg were performed, in which 99.0 + or - 4.6 percent of the smaller and 97.6 +/- 11.3 percent of the greater mass were recovered. In 45 healthy adult males plasma concentrations between 0.44 and 1.80 microgram/l were found. The median was 1.06 microgram/l. Stimulation of the Leydig cells with human chorionic gonadotropin (HCG) increased plasma concentrations by 93 percent (average in 12 males). Thereapeutic castration in 8 men caused an average decrease of 55.4 percent in plasma values.