Inhibition of nuclear testosterone 5 alpha-reductase in rat ventral prostate by estrogens and anti-androgens

The activity of testosterone 5α-reductase in purified nuclei of rat ventral prostate was inhibited by addition of estradiol-17β, estrone or estriol in vitro. Rate of the inhibition of the enzyme activity by these estrogens was of similar degree. Therefore, this inhibitory effect does not seem to be correlated to their estrogenic potency.Effect of three anti-androgens (Ro 2-7239, SK & F 7690 and TSAA 291) on the activity of testosterone 5α-reductase was also examined and it was revealed that SK & F 7690 and TSAA 291 showed the inhibitory effect on the enzyme activity.