RADIOIMMUNOASSAY FOR THE TESTOSTERONE 5-ALPHA-REDUCTASE INHIBITOR TUROSTERIDE IN BIOLOGICAL-FLUIDS

An antiserum against turosteride (code name FCE 26073), a potent testo sterone 5 alpha-reductase inhibitor, has been raised in rabbits by imm unization with an immunogen produced by conjugation of a derivative of FCE 26073 (FCE 27424) to bovine serum albumin. The antiserum was able to distinguish FCE 26073 from its derivatives modified at the 17 beta position and from all the endogenous steroids tested. A radioimmunoas say for the determination of FCE 26073 in human plasma and urine was d eveloped using this antiserum and tritium labeled turosteride. FCE 260 73 was extracted from 50 mu l of plasma or 25 mu l of urine using ethy l-ether with a recovery greater than 90%. Using this procedure it was possible to achieve a final limit of quantitation of 142 pg/ml in plas ma and 284 pg/ml in urine. The assay was validated in terms of reprodu cibility, accuracy and precision in the range 3.9 - 250 pg/50 mu l of plasma and 25 mu l of urine. The plasma concentration of FCE 26073 in a healthy male volunteer who received 0.2 mg of the drug was measured using the radioimmunoassay.