Identification of an androgen receptor in the cytosol of the female Mastomys prostate.

An in vivo and in vitro study was carried out on the prostate from the female Praomys (Mastomys) natalensis to identify and characterize the binding of androgens within the cytoplasm. The labelled cytosol was prepared and subjected to gel exclusion chromatography and density gradient centrifugation. A macromolecular protein associated with the radioactivity was isolated on Sephadex G-200. Subsequent analysis of the steroid receptor complex showed that the major part of the radioactive steroid (64 percent) was dihydrotestosterone. This binding was inhibited by unlabelled testosterone and could not be demonstrated in liver cytosol. Characterization of this dihydrotestosterone receptor complex revealed a sedimentation coefficient of 4.6 s in the presence of a high salt solution (0.4 M KCl). The complex aggregated in the absence of 0.4 M KCl and sedimented preferentially from 5.6-7.4 s together with polydisperse aggregates of higher sedimentation coefficients. The use of this animal as an experimental model for hormonal studies on the prostate is suggested.