Studies on the in vivo hormonal control of rat prostatic testosterone 4-ene-5α-reductase activity

Abstract

Because recent reports indicate that the enzymatic 4-ene-5α-reduction of testosterone is an important step in the expression of androgenic activity in the prostate, we have investigated the effects of several hormonal situations on the activity of this enzyme in adult rat prostate. Both specific (pmol testosterone 5α-metabolites formed/mg protein/60 min) and total (pmol testosterone 5α-metabolites formed/rat prostate/ 60 min) activities were measured. Experimental groups subjected to castration or adrenalectomy showed decreased specific and total activities when compared to intact controls. In the hypophysectomized control group the specific activity was increased while the total activity was decreased as compared to intact controls. Estradiol administration for four days to each of the four groups resulted in decreases in both specific and total activities when compared to their group controls. Testosterone administration for four days to each of the four groups resulted in increases in both specific and total activities as compared to their group controls. Combined estradiol and testosterone administration, when compared to the effects of testosterone alone, resulted in no essential change in the intact group, an increase in the castrated group and decreases in the hypophysectomized and adrenalectomized groups. Ovine prolactin administration alone or in combination with estradiol or testosterone or both resulted in no consistent change in enzyme activity in either the intact or hypophysectomized groups. Our results suggest that a number of hormones can modify the activity of prostatic testosterone 4-ene-5α-reductase activity and hence may influence the growth and activity of the prostate.