A direct radioimmunoassay for 11-deoxycortisol

A rapid, sensitive and highly specific radioimmunoassay (RIA) for 11-deoxycortisol has been developed and used for the measurement of serum concentrations.Antisera were raised using 11-deoxycortisol-3-carboxymethyloxime-bovine serum albumin as immunogen and showed minimal cross reaction with related steroids. 11-Deoxycortisol-3-carboxymethyloxime was coupled to ¹²⁵I-iodohistamine to produce a labelled antigen of high specific activity (s.a. 680 Ci/mmol). The assay was performed for 1h at room temperature and pH 4.Results were correlated with those after extraction, high pressure liquid chromatography and RIA of serum samples (y = 0.78x + 36.9; r = 0.97, p<0.001). The accuracy of the method was satisfactory (y = 1.00x ? 0.61; r = 0.95; p<0.001). Assay sensitivity was 0.3 nmol/1. 11-Deoxycortisol concentrations in normal subjects at 09.00h were 26 ? 46 nmol/1 $\text{(37.2 ± 5.7;}\text{x}\text{± 1}\text{S.D.}\text{)}$.The assay should facilitate the investigation of patients with possible abnormalities of adrenocortical function.