title: Differential suppression of progesterone receptors by progesterone in the reproductive tract of female macaques.
abstract: Ovariectomized cynomolgus macaques were treated with implants of estradiol (E2) for 14 days. Some animals then received an additional implant of progesterone (P) for 7-14 more days. After treatment with either E2 alone or with E2 plus P we removed the reproductive tracts and measured nuclear and cytosolic P receptors by exchange assay. In addition we used steroid radioimmunoassays(RIA) to measure levels of E2 and P in parallel aliquots of the nuclear and cytosolic fractions. P treatment reduced the concentrations of E2 in nuclear and cytosolic fractions in the cervix, endometrium, myometrium and oviduct compared to the amounts present after 14 days of E2; these data are consistent with many reports that P treatment significantly lowers the amount of nuclear and cytosolic estrogen receptors in all of these tissues. In the oviduct, myometrium and cervix both cytosolic and nuclear P receptor levels were lowered during P action. In the endometrium, however, P treatment reduced the amount of P receptor only in the cytosolic but not the nuclear fraction. RIA determinations of the amount of P retained in nuclear fractions of the P-treated animals indicate that P levels were significantly elevated only in the nuclei obtained from endometrium. This specific increase in the retention of P by endometrial nuclei during P action is consistent with the specific retention of P receptor by endometrial nuclei. These results lead to the unexpected conclusion that the stimulatory effects of P as expressed in the maintenance of the progestational state in the primate endometrium may require higher levels of occupied nuclear P receptor than do the suppressive effects of P as expressed in oviductal atrophy, diminished cervical secretion and myometrial quieting.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002584:Cervix Uteri / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004717:Endometrium / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D005187:Fallopian Tubes / Q000378:metabolism; D005260:Female; D005836:Genitalia, Female / Q000187:drug effects / Q000378:metabolism*; D008252:Macaca fascicularis; D009215:Myometrium / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism / Q000494:pharmacology*; D011980:Receptors, Progesterone / Q000187:drug effects*
chemical_list: D011980:Receptors, Progesterone; D011374:Progesterone; D004958:Estradiol