17β-estradiol enhances androgen-induced prostate growth in the castrate dog to a degree comparable to that seen in spontaneous prostatic hypertrophy. To investigate the mechanism of this synergism, cytosol androgen binding was measured by a density gradient technique in prostates of control and 17β-estradiol-treated castrate dogs. [3H]Dihydrotestosterone was bound principally to a moiety that averaged 8.6S in size. Approximately twofold enhancement of this binding by 17β-estradiol was demonstrable after 1 wk of treatment with 750 μg/wk and after 3 wk with 75 μg/wk. Under conditions in which binding in the 8S region was demonstrable with dihydrotestosterone and testosterone no binding of 3α-androstanediol or progesterone was detectable. Thus, enhancement by 17β-estradiol of a prostate cytosol androgen-binding protein occurs under circumstances in which 17β-estradiol enhances androgen-mediated prostatic growth.
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