title: Estrogen-sensitive progestin-binding sites in the female rat brain and pituitary.
abstract: The following properties of the cytoplasmic progestin receptor were studied in the hypothalamus, cortex, pituitary and uterus of the estrogen-primed castrated adult female rat using the highly potent progestin R 5020 (promegestone). (a) Sedimentation pattern. In sucrose density gradients, the R 5020-progestin receptor complex sedimented with a coefficient of about 6 to 7S. (b) Binding parameters. R 5020 bound to the progestin receptor with an intrinsic dissociation constant of about 10(-9) M as measured by a Dextran-coated charcoal (DCC) technique. The number of binding sites, however, differed widely. (c) Specificity. Only progestins competed for [3H]R 5020 binding. (d) Estrogen-dependency. In both immature and castrated adult rats, estrogen administration increased the number of R 5020-specific binding sites, assayed in vitro by a DCC technique, in the uterus, pituitary and hypothalamus, but not in the amygdala, hippocampus nor in the cortex. The increase was maximum between 40 and 48 h after priming with the potent estrogen, moxestrol, and could not be induced by androgens nor by progestins.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D002369:Castration; D002499:Centrifugation, Density Gradient; D002540:Cerebral Cortex / Q000378:metabolism; D045166:Estradiol Congeners / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D009649:Norpregnadienes / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D011397:Promegestone / Q000378:metabolism*; D051381:Rats; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism*; D014599:Uterus / Q000378:metabolism
chemical_list: D045166:Estradiol Congeners; D009649:Norpregnadienes; D011980:Receptors, Progesterone; D011397:Promegestone