In vivo effects of steroid hormones on the testosterone 5alpha-reductase in skin.

We have studied the hormonal regulation of the levels of testosterone 5alpha-reductase in rat skin by performing surgical manipulations (gonadectomy and/or adrenalectomy) of the rats and by steroid administration to ovariectomized- adrenalectomized rats. Castration significantly increases (P smaller than 0.01) the enzyme activity in the sole of the foot but not in the thoracic skin of male rats. In female rats, significant elevations of the enzyme activity are observed in the thoracic skin (P smaller than 0.01) and in the sole of the foot (P smaller than 0.05) after ovariectomy. Estrogen administration decreases the enzyme activity in thoracic skin, tail skin and vulvar skin of ovariectomized-adrenalectomized rats. Testosterone and dihydrotestosterone decrease the activity in the sole of the foot and increase the activity in vulvar skin. Progesterone and corticosterone administration produce no significant effects in the four skin types studied.