title: Diurnal variations in estradiol binding site concentrations in the hypothalamus, pituitary and uterus of prepuberal rats.
abstract: Available cytosolic estradiol binding sites (EBS) were estimated at 6 h intervals over a 24 h period in individual extracts of uteri, pituitaries and hypothalami from intact, ovariectomized or hypophysectomized 28-day old rats, maintained from birth in a 12 h light-12 h dark photoperiod. Plasma estrogen levels were also recorded, in intact rats, they displayed a 20% rise during daytime. In the uterus and pituitary of ovariectomized rats EBS concentrations exceeded by one third those of intact controls. In intact animals, significant diurnal variations in EBS were observed in both these tissues, with increased daytime levels. These variations appeared to depend on the amount of estrogen in the plasma, as they were not observed in spayed rats. No diurnal variations in EBS were apparent in the hypothalamus of intact animals, but they did occur in ovariectomized rats, and even more significantly in hypophysectomized rats, although the latter had lower EBS concentrations than spayed animals. These variations were presumed to result from the interference of pituitary-controlled hormones other than estrogens in the regulation of EBS levels.
mesh_terms: D000818:Animals; D002369:Castration; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood; D004958:Estradiol / Q000097:blood / Q000378:metabolism*; D005260:Female; D007016:Hypophysectomy; D007031:Hypothalamus / Q000378:metabolism*; D009928:Organ Specificity; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen / Q000378:metabolism*; D012741:Sexual Maturation; D014599:Uterus / Q000378:metabolism*
chemical_list: D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol; D003345:Corticosterone