Sex differences in adrenocortical structure and function. IV. Effects of postpubertal gonadectomy and sex hormones on adrenal steroid 5alpha-reductase activity in the rat.

Studies on the effects of gonadectomy and gonadal hormones on adrenal 5alpha-reductase activity in the rat were performed. In rats of both sexes postpubertal gonadectomy is followed by an increase in adrenal 5alpha-reductase activity. The enzyme activity gradually increases during 6 postoperative weeks. Replacement of testosterone or estradiol to gonadectomized rats within 5 days lowers the enzyme activity to the level observed in intact control rats. Likewise, testosterone injected to ovariectomized rats and estradiol administered to orchiectomized animals within 5 days reversed the effect of gonadectomy on 5alpha-reductase. In all experiments the temporal changes in 5alpha-reductase activity were similar. By contrast, the weight of seminal vesicles of gonadectomized rats was normalized after 7 days of testosterone action whereas the highest uterine weight was found 3 days post depot-estradiol injection. Regarding temporal changes in 5alpha-reductase activity the experiments revealed similar inhibitory action of testosterone and estradiol. This action probably depends on the inhibition of enzyme synthesis by gonadal hormones. Moreover, greater sensitivity of adrenals of gonadectomized rats to testosterone, if compared with seminal vesicles, was observed.