Inhibition of the nuclear dihydrotestosterone receptor complex from rat ventral prostate by antiandrogens and stilboestrol

Abstract The inhibitory effects of stilboestrol and representatives from three main classes of antiandrogens on the dihydrotestosterone receptor complex isolated from the nuclei of rat ventral prostate were compared. After labelling of the tissue in vivo or in vitro with [ 3 H]testosterone in the presence or absence of test drugs, the nuclear extracts were prepared and the inhibitory effect on the steroid-receptor complex was evaluated. Equimolar doses (1 μmol/100 g body weight) of cyproterone acetate, chlormadinone acetate, SC 9022 and flutamide inhibited the binding of dihydrotestosterone to the receptor complex by 48–54%, whereas in the in vitro studies an equimolar concentration (0.1 μM) inhibited the binding by 45–58% with the exception of flutamide which had no effect. Under these experimental conditions stilboestrol had no effect on the binding of dihydrotestosterone to the nuclear receptor.