Changes in brain, pituitary and uterine cytoplasmic oestrogen receptors induced by oestradiol-17beta in the ovariectomized rat

Abstract

The oestrogen specific, high-affinity cytosol receptor receptor (HAR) from amygdala, anterior, middle and posterior hypothalamus, pituitary and uterus was studied in the ovariectomized rat. A single in-vivo injection of oestradiol-17beta produced significant changes in both the tissue HAR concentrations and the apparent dissociation constants (Kd) determined in vitro. Four hours after oestradiol-17beta treatment (20 mug/kg), the HAR concentration was depleted in all tissues except the posterior hypothalamus. A lower dose of oestradiol-17beta (4 mug/kg) produced similar changes in HAR concentration with the exception of those in the amygdala and posterior hypothalamus. Twenty-four hours after oestradiol-17beta, HAR concentrations had returned to pre-injection levels in all tissues except the uterus. The uterine HAR concentrations were raised after both doses of oestradiol-17beta. The apparent tissue cytosol Kd values were decreased by both doses of oestradiol-17beta. The results suggest that brain, pituitary and uterine oestrogen cytosol HARs react to plasma oestrogen in a manner predictable by the steroid receptor hypothesis. The oestradiol-17beta-induced differential effects upon the tissue cytosol concentration may contribute to the overall spectrum of action of oestrogen in the central and peripheral reproductive processes.

PIP: Changes in brain, pituitary, and uterine cytoplasmic estrogen receptors induced by estradiol-17beta were studied in the ovariectomized rat. A single in vivo injection of estradiol-17beta produced marked changes in both the tissue high-affinity cytosol receptor (HAR) concentrations and the apparent dissociation constants determined in vitro. 4 hours after estradiol-17beta treatment (20 mcg/kg), the HAR concentration was depleted in all tissues except the posterior hypothalamus. 4 mcg/kg of estradiol-17beta produced similar changesin HAR concentration with the exception of those in the amygdala and posterior hypothalamus. 24 hours after estradiol-17beta HAR concentrations had returned to preinjection levels in all tissues except the uterus. the uterine HAR concentrations were raised after both doses and the apparent tissue cytosol dissociation constant values were decreased by both doses. These data suggest that brain, pituitary and uterine estrogen cytosol HARs react to plasma estrogen in a manner predictable by the steroid receptor hypothesis. The induced differential effects upon the tissue cytosol concentration may contribute to the overall spectrum of action of estrogen in the central and peripheral reproductive process.