title: Ovariectomy-evoked increase in gonadotropin releasing hormone receptor parallels its messenger RNA level, but does not correlate with stimulated gonadotropin release.
abstract: The amount of gonadotropin releasing hormone receptor (GnRH-R) in the anterior pituitary changes during the rat estrous cycle; in addition, it is chronically increased for several weeks in response to ovariectomy. The present study was undertaken to investigate these changes in relation to the concentrations of GnRH-R mRNA, gonadotropins and luteinizing hormone-beta (LH-beta) subunit in serum and the pituitary gland, as well as hypothalamic GnRH. GnRH-R concentrations on the day of estrus were significantly lower than that at diestrus (30% lower during 2 d), its mRNA decreased even further (by 60%), but there were no significant changes in gonadotropin. Ovariectomy increased GnRH-R significantly (by 30% during 2 wk) in parallel with receptor mRNA and with pituitary LH and LH-beta, but induced an earlier increase in serum gonadotropins. Our results suggest that transcriptional activity is more intimately linked to the number of GnRH-R in the long-term increase after ovariectomy than in the short-term change during the estrous cycle, and that the increased GnRH-R is not a major factor in ovariectomy-stimulated gonadotropin release.
authors.affiliation: Department of Obstetrics and Gynecology, School of Medicine, Keio University, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Saito
authors.forename: S
authors.initials: S
authors.lastname: Izumi
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: S
authors.initials: S
authors.lastname: Saitoh
authors.forename: T
authors.initials: T
authors.lastname: Makino
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: S
authors.initials: S
authors.lastname: Nozawa
authors.forename: K
authors.initials: K
authors.lastname: Takamatsu
mesh_terms: D000818:Animals; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D010052:Ovariectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011966:Receptors, LHRH / Q000235:genetics* / Q000378:metabolism*
chemical_list: D006065:Gonadotropins, Pituitary; D012333:RNA, Messenger; D011966:Receptors, LHRH; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone