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 125 I-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 less than 0.001). The accuracy of the method was satisfactory (y = 1.00x - 0.61; r= 0.95; p less than 0.001). Assay sensitivity was 0.3 nmol/l. 11-Deoxycortisol concentrations in normal subjects at 09.OOh were 26-46 nmol/l (37.2 +/- 5.7; x- +/- 1 S.D.). The assay should facilitate the investigation of patients with possible abnormalities of adrenocortical function.