Androgen receptors in rat ventral prostate microsomes

Abstract

The androgens 17β-hydroxy-5α-androstane-3-one (androstanolone, dihydrotestosterone) and 5α-androstane-3β,17β-diol (3β-androstanediol) bind to a single specific component of the “micrisomes” (105 000× g sediment) of adult rat ventral prostate. The apparent association constant is 2.5±0.9 · 10 10 M −1 (mean ±S.E.) for androstanolone and 6.5±4.4 · 10 10 M −1 for 3β-androstanediol. The number of binding sites approaches 10 fmoles/mg microsomal protiens. The specific binding is inhibited by proteolytic enzymes and-SH blocking agents. Competition studies show that testosterone and 5α-androstane-3α,17β-diol are weak competitors whereas estradiol, progesterone and cortisol are ineffective. No such high affinity binding was observed in rat liver microsomes. On the basis of apparent affinity and steroid specificity determinations, the microsomal receptor seems different from the androgen receptor previously described in rat ventral prostate cytosol.