Binding and effects of 5 alpha-androstane-3 beta,17 beta-diol in the male rat pituitary

5 alpha-androstane-3 beta,17 beta-diol (Adiol) binds to cytosol proteins from male rat pituitary with a relatively high affinity (KD = 15 +/- 6 nM) and a low capacity (n = 92 +/- 8 fmol/mg protein). These saturable proteins which bind Adiol are characterized as estrogen receptor. This conclusion was based on the binding characteristics, the binding stereospecificity and the sedimentation coefficient in sucrose linear gradients. Moreover. Adiol induces, in vivo, the nuclear translocation of estrogen receptor and some effects of estrogen action. It is efficient to induce progesterone receptor and to increase pituitary protein content but inefficient to increase DNA synthesis. Results suggest a mechanism of Adiol action in the male rat pituitary similar to that observed with androgens in other target tissues. Moreover, the study of Adiol and 17 beta-estradiol binding suggests two forms of estrogen receptor in the cytosol from male rat pituitary. The maximal concentration of binding sites was observed at 22-30 days of age for E2 and at 37-42 days of age for Adiol. On the other hand, the nuclear ontogenic pattern suggested a single class of binding sites for E2 and Adiol in the pituitary nuclei.