title: Regulation of gonadotropin subunit transcription after ovariectomy in the rat: measurement of subunit primary transcripts reveals differential roles of GnRH and inhibin.
abstract: The aim of this study was to determine if the changes in gonadotropin subunit gene expression following ovariectomy reflect transcriptional and/or posttranscriptional regulation by GnRH or inhibin. Subunit transcription rates were determined by recently developed quantitative RT-PCR for subunit primary transcripts (as an indicator of gene transcription), which allow us to measure both mRNA and PT from RNA extracted from a single pituitary. Following ovariectomy, LHbeta PT concentrations increased 2- to 3-fold between 72 h and 7 d, paralleling changes in serum LH and LHbeta mRNA. In contrast, serum FSH, FSHbeta mRNA, and FSHbeta PT concentrations were 6- to 9-fold greater 12-24 h after ovariectomy followed by an additional 2.5-fold increase at 72 h. Although alpha RNA was elevated at 72 h after ovariectomy, alpha-primary transcript did not change. GnRH antagonist prevented the increase in LHbeta-PT at 72 h, but had no effect on the increase in FSHbetaPT at 12 h and was only partially effective at 72 h. The acute GnRH-independent increase in FSHbeta-primary transcript after ovariectomy could be duplicated by the administration of inhibin antiserum to intact rats; inhibin-alpha antiserum did not affect LHbeta-primary transcript, but increased FSHbeta-primary transcript concentrations 8- to 11-fold. The half-disappearance rates of LHbeta and FSHbeta primary transcripts were measured after GnRH blockade or administration of recombinant human inhibin A. The half-disappearance times for LHbeta and FSHbeta primary transcripts following GnRH blockade were 13 and 17 min, respectively; the mRNAs did not change. The effects of inhibin were specific for FSHbeta; 60 min after inhibin FSHbeta-primary transcript was undetectable with a half-disappearance time of 19 min, additionally FSHbeta mRNA levels also fell with a half-life of 94 min. In conclusion, these data support previous evidence that GnRH regulates gonadotropin gene expression primarily at the level of transcription. However, the acute increase in FSHbeta-primary transcript after ovariectomy or immunoneutralization of inhibin-alpha, and the rapid fall in FSHbeta-primary transcript following rh inhibin, provide novel evidence that inhibin suppresses FSHbeta gene transcription in addition to its action in regulating FSHbeta mRNA stability.
authors.affiliation: Division of Endocrinology, Department of Internal Medicine, and the Center for Research in Reproduction, University of Virginia, Charlottesville, Virginia 22908, USA. llb3k@virginia.edu
authors.forename: L L
authors.initials: LL
authors.lastname: Burger
authors.forename: A C
authors.initials: AC
authors.lastname: Dalkin
authors.forename: K W
authors.initials: KW
authors.lastname: Aylor
authors.forename: L J
authors.initials: LJ
authors.lastname: Workman
authors.forename: D J
authors.initials: DJ
authors.lastname: Haisenleder
authors.forename: J C
authors.initials: JC
authors.lastname: Marshall
mesh_terms: D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000235:genetics*; D037201:Follicle Stimulating Hormone, beta Subunit; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology; D007265:Inhibins / Q000494:pharmacology / Q000502:physiology; D007986:Luteinizing Hormone / Q000235:genetics*; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D037201:Follicle Stimulating Hormone, beta Subunit; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007987:Gonadotropin-Releasing Hormone; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone