Catecholestrogens and release of anterior pituitary gland hormones. II. Prolactin

We investigated the effects of the peripheral administration of 17 beta-estradiol (E2), estrone (E1), and the catecholestrogens, 2-hydroxyestradiol (2-OHE2) and 2-hydroxyestrone, (2-OHE1), on anterior pituitary gland PRL release in the prepuberal rat. Steroids in oil were injected sc into 25-day-old female and 35- to 40-day-old male rats. The injection of E2, E1, or 2-OHE2, but not of 2-OHE, caused a surge in serum PRL levels in female rats 48 h later, during the afternoon hours. Only E1 induced a PRL surge 24 h after injection. In male rats, the injection of E1 or 2-OHE2, but not of 2-OHE1, elevated serum PRL levels on a chronic basis. The results suggest that 2-OHE1 plays no discernible role in PRL release in either sex, but that 2-OHE2 might play a role in the tonic release of PRL in the male and in the preovulatory release of PRL in the female.