title: Regulation of cytosol and nuclear progesterone receptors in rabbit uterus by estrogen, antiestrogen and progesterone administration.
abstract: A synthetic progestin, 16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione (ORG 2058), was utilized to measure progesterone receptors from the rabbit uterus. This steroid has a high affinity for both cytosol and nuclear receptors, with KD values of 1.2 nM (at 0--4 degrees C) and 2.3 nM (at 15 degrees C), respectively. Administration of estradiol-17 beta or a non-steroidal antiestrogen, tamoxifen, for 5 days to estrous rabbits led to a progressive rise in the cytosol receptor levels: from 34,000 to 120,000 (estradiol-17 beta) and 80,000 (tamoxifen) receptors/cell, without any major influence on the nuclear receptor content. A single intravenous injection of progesterone (5 mg/kg) elicited a 3-fold increase in the mean nuclear receptor content at 30 min after injection (from 18,000 to 48,000 receptors/nucleus). Nuclear receptor accumulation was short-lived and returned to control levels within 4 h after treatment. A second dose of progesterone given 24 h later doubled the nuclear receptor level (from 18,000 to 35,000 receptors/nucleus). The concomitant decline in the cytosol receptor content was twice that accounted for by the nuclear receptor accumulation (70,000 vs. 30,000, and 40,000 vs. 17,000 receptors/cell, after the first and second progesterone injection, respectively). Following progesterone administration, the cytosol receptor level reached a nadir by 30 min, exhibited minimal replenishment within the ensuing 24 h, and remained at approx. 50% of the pretreatment values. After a single dose or two consecutive doses of progesterone, total uterine progesterone receptor content declined to about 60% of the level prior to each dose, a nadir being reached at 2 h after treatment.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D009652:Norpregnenes / Q000378:metabolism; D011282:Pregnenediones / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology*; D045167:Progesterone Congeners / Q000378:metabolism*; D011817:Rabbits; D011980:Receptors, Progesterone / Q000187:drug effects* / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D009652:Norpregnenes; D011282:Pregnenediones; D045167:Progesterone Congeners; D011980:Receptors, Progesterone; D013629:Tamoxifen; C020175:16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione; D011374:Progesterone; D004958:Estradiol