Abstract

The administration of 5-alpha-dihydrotestosterone (5-alpha-DHT) and dexamethasone has been shown to attenuate estrogen-induced prolactin release in the estrogen-primed rat. Therefore, the effect of these compounds was studied on anterior pituitary and uterine estrogen receptors. Injection of 0.8 mg/kg body weight of 5-alpha-DHT to ovariectomized adult rats treated with 2-mu-g estradiol/d for 4 days resulted in a significant decrease in occupied nuclear estrogen receptors of the anterior pituitary but not the uterus. Estrogen priming was essential for 5-alpha-DHT effect on occupied nuclear anterior pituitary estrogen receptors because this effect did not occur in ovariectomized vehicle-treated control animals. The administration of 1 mg/kg body weight of dexamethasone brought about a decrease in uterine but not anterior pituitary nuclear estradiol receptors. These results provide further evidence that the regulation of estrogen receptor dynamics is different in the anterior pituitary and the uterus and that different steroids can exert tissue-specific effects.