title: Estrogen enhances endometrial estrogen receptor gene expression by a posttranscriptional mechanism in the ovariectomized ewe.
abstract: Prior influence of estrogen is required for many physiological effects of steroid hormones. This study addresses positive autoregulation of estrogen receptor gene expression in endometrium. Groups of ovariectomized ewes (n = 6) were treated with a single i.m. injection of 50 micrograms 17 beta-estradiol for 6, 12, 24, or 48 h or of vehicle for 24 h (control) prior to collection of endometrium. Three ewes received a regimen of estradiol-progesterone-estradiol (EPE) designed to mimic the estrous cycle. Northern analysis of endometrial RNA using an ovine estrogen receptor complementary RNA probe indicated that estradiol increased (p < 0.0001) estrogen receptor messenger RNA abundance over time to be 5-fold greater at 24 h postinjection. This effect also occurred after a period of progesterone dominance in EPE ewes (p < 0.05). Ribonuclease protection assays with a complementary RNA probe for the ovine progesterone receptor demonstrated that estradiol treatment increased progesterone receptor messenger RNA abundance at 48 h (p < 0.005). Nuclear runoff analyses indicated that whereas estradiol enhanced the transcription rates of progesterone receptor (p < 0.1) and 28S ribosomal RNA genes (p < 0.002), activity of the estrogen receptor gene was unchanged (p > 0.25). These results suggest that a physiological dose of estradiol, similar to the preovulatory surge of estrogen, up-regulates endometrial estrogen receptor gene expression by a posttranscriptional mechanism.
authors.affiliation: Department of Animal Science, Texas A & M University, College Station 77843-2471, USA.
authors.forename: N H
authors.initials: NH
authors.lastname: Ing
authors.forename: T E
authors.initials: TE
authors.lastname: Spencer
authors.forename: F W
authors.initials: FW
authors.lastname: Bazer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004717:Endometrium / Q000187:drug effects / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D008969:Molecular Sequence Data; D010052:Ovariectomy; D015347:RNA Probes; D012333:RNA, Messenger / Q000378:metabolism; D011960:Receptors, Estrogen / Q000737:chemistry / Q000235:genetics*; D011980:Receptors, Progesterone / Q000737:chemistry / Q000235:genetics; D012756:Sheep; D014158:Transcription, Genetic
chemical_list: D015347:RNA Probes; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D004958:Estradiol