Alterations in the prolactin secretion in streptozotocin-induced diabetic rats. Correlation with pituitary and hypothalamus estradiol receptors.

The present study examined the effects of streptozotocin-induced diabetes on prolactin (Prl) secretion and its correlation with estrogen receptor levels in the anterior pituitary and hypothalamus. Prl was measured in adult ovariectomized rats and after estradiol treatment (10 micrograms estradiol benzoate (Eb) 48, 24 and 1 h before experiments) or acute TRH administration (4 micrograms/kg body weight). Substantial decreases in estradiol- and TRH-induced Prl release were observed in diabetic rats. Insulin therapy was able to restore this response. Measurement of nuclear estradiol receptors by exchange assay in the pituitary of Eb-treated rats revealed a significant reduction in receptor levels in the diabetic group and a restoration to normal values in insulin-treated diabetic rats. Similar results were obtained by measuring total pituitary receptor content (cytosolic plus nuclear receptors). No significant changes were observed in nuclear hypothalamic estradiol receptors. However, the number of total hypothalamic estradiol receptors was diminished in diabetic rats although the translocation was proportionally greater in these animals. These results indicate that the disrupted reproductive functions described in streptozotocin diabetic rats may be due, at least in part, to deficiencies in Prl secretion and pituitary estradiol action.