Synthesis of new steroid haptens for radioimmunoassay. Part I. 15beta-Carboxyethylmercaptotestosterone-bovine serum albumin conjugate. Measurement of testosterone in male plasma without chromatography

Abstract

A radioimmunoassay (RIA) procedure has been developed for measurement of testosterone in male plasma after ether:chloroform (4:1) extraction of the plasma sample without resorting to chromatography. The highly specific anti-testosterone serum was generated from both rabbits and sheep immunized with 15beta-carboxyethylmercapto-testosterone-BSA conjugate. The synthesis of 15beta-carboxyethylmercaptotestosterone and the preparation of its BSA conjugate are described. The high affinity (Ka=2.38 X 10(9) liters/mole) antiserum binds 50% of 50 picograms of tritiated testosterone at working dilutions of 1:100,000 to 1:200,000. Both 5alpha and 5beta-dihydrotestosterone compounds exhibited less than 2% cross-reaction. The only other steroids that showed minor cross-reaction were 11beta-hydroxytestosterone (3.8%), progesterone (2.1%), corticosterone (1.6%), and deoxycorticosterone (7.7%).