A soluble androgen receptor in the cytoplasm of the male Mastomys prostate.

A steroid receptor protein was isolated from the cytoplasmic fraction of Mastomys prostate. Following in vivo and in vitro labelling of the tissue with tritiated testosterone or dihydrotestosterone, samples were analysed by gel exclusion chromatography or sucrose density gradient centrifugation. A steroid receptor complex was isolated on Sephadex G-200. Analysis of the steroids associated with this complex showed that the major part of the bound radioactivity was 5 alpha-dihydrotestosterone. The binding was inhibited by unlabelled testosterone and could not be demonstrated in the liver cytosol. Using sucrose density gradient centrifugation, the dihydrotestosterone receptor complex sedimented at 5.6 s together with heavier aggregates. In the presence of 0.4 M KCl a single complex was sedimented at 4.6 s. The results demonstrate a receptor protein in the cytosol of the Mastomys prostate which binds to dihydrotestosterone and is comparable to that of rat prostate.