In the immature castrate rat, the antiandrogens cyproterone (C) (30 or 150 mg/kg) and cyproterone acetate (CA) (10 or 50 mg/kg) inhibited the growth of the ventral prostate and seminal vesicles that was induced by dehydroepiandrosterone (DHA), androstenedione (A), or testosterone (T) injected at various doses for 7 days. When the lowest doses of androgen were used (DHA 0.4 mg, A 0.02 mg, and T 0.015 mg), C and CA were often able to maintain the weights of target organs at castrate levels. CA was about 3 times more potent than C in antiandrogenic activity. CA also significantly inhibited the increase in prostatic weight that occurred after 14 days of administration of ACTH (20 U/day), prolactin (1 mg/day) plus ACTH (5 mg/day), or prolactin (1 mg/day) plus DHA (0.2 mg/day). It is concluded that C and CA can inhibit the known extratesticular stimuli to prostatic growth in the rat. These stimuli may all be mediated by an androgendependent cellular response.
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