The regulation of the 5α-reductase that converts testosterone to dihydrotestosterone in rat ventral prostate has been investigated by studying the effect of the administration of androgens to castrate animals for varying periods of time. Testosterone propionate treatment resulted in a 7-fold increase above the normal level in the total activity of the enzyme per prostate and caused a similar increase in the specific activity of the enzyme both in homogenate and in the nucleus. Thyroid, adrenal, pituitary, and estrogenic hormones do not appear to play a major role in the mediation of this androgenic control. Finally, on the basis of time sequence studies following testosterone propionate administration and of studies comparing the effects of different steroids on prostate growth and enzyme content, it has been concluded that the enzyme activity correlates with the growth response of the prostate to androgen treatment.
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