CHANGES IN BRAIN, PITUITARY AND UTERINE CYTOPLASMIC OESTROGEN RECEPTORS INDUCED BY OESTRADIOL-17β IN THE OVARIECTOMIZED RAT

Abstract

SUMMARY: The oestrogen specific, high-affinity cytosol 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-17β produced significant changes in both the tissue HAR concentrations and the apparent dissociation constants (K_d) determined in vitro. Four hours after oestradiol-17β treatment (20 μg/kg), the HAR concentration was depleted in all tissues except the posterior hypothalamus. A lower dose of oestradiol-17β (4 μg/kg) produced similar changes in HAR concentration with the exception of those in the amygdala and posterior hypothalamus. Twenty-four hours after oestradiol-17β, 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-17β. The apparent tissue cytosol K_d values were decreased by both doses of oestradiol-17β. 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-17β-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.