Studies on the interaction of 5 alpha-androstane-3 beta, 17 beta-diol with the testicular estrogen receptor.

5 alpha-Androstane-3 beta,17 beta-diol (3 beta-diol) was observed to inhibit [3H]estradiol ([3H]E2) binding to testicular cytosol preparations from both immature and mature rats with a potency of 1% that of diethylstilbestrol. The nature of the inhibition of [3H]E2 binding by 3 beta-diol was shown to be competitive with a KI of approximately 12 nM. This high competitive potency for a C19 steroid required both 3 beta- and 17-hydroxyl groups,, and reduced C5 position to inhibit E2 binding. Despite the interaction of 3 beta-diol with E2 receptor in vitro, injection of immature rats with 25 or 250 microgram 3 beta-diol 1-6 h before autopsy did not occupy or deplete the testicular cytoplasmic E2 receptor. When administered to immature female rats, 3 beta-diol did not show estrogenic agonistic or antagonistic activity in the uterus. These results suggest that the interaction of 3 beta-diol with the testicular receptor may be of little physiological significance.