title: Seasonal cyclicity of secretogranin-II expression and its modulation by sex steroids and GnRH in the female goldfish pituitary.
abstract: The secretory vesicle protein secretogranin-II (SgII), a precursor for the bioactive peptide secretoneurin, is expressed at all levels of the goldfish reproductive axis, including the hypothalamus, pituitary and ovaries. These findings led us to hypothesize that SgII is involved in reproduction and is physiologically regulated. We investigated the effects of different sex steroids on pituitary SgII expression throughout the seasonal reproductive cycle of the female goldfish, as well as the effects of GnRH and testosterone on pituitary LHbeta subunit, GH, and SgII expression in sexually recrudescent female fish using northern blot analysis. We demonstrated that SgII expression levels vary seasonally, with levels being highest in winter and lowest in spring. Sex steroids did not alter SgII expression at any of the time periods studied. In sexually mature goldfish, injection of a GnRH agonist stimulated the expression of LHbeta and SgII specifically in the pars distalis but not the neurointermediate lobe of the pituitary. Although testosterone alone did not alter the expression of either of these genes, it did abolish the stimulatory effects of GnRH on both LHbeta and SgII expression. This represents the first study where testosterone is shown to modulate SgII expression in the pituitary.
authors.affiliation: Department of Biology, University of Ottawa Centre for Advanced Research in Environmental Genomics (CAREG), MacDonald Hall, Ottawa, Ont., Canada K1N 6N5.
authors.forename: M
authors.initials: M
authors.lastname: Samia
authors.forename: K E
authors.initials: KE
authors.lastname: Larivière
authors.forename: M H
authors.initials: MH
authors.lastname: Rochon
authors.forename: B M
authors.initials: BM
authors.lastname: Hibbert
authors.forename: A
authors.initials: A
authors.lastname: Basak
authors.forename: V L
authors.initials: VL
authors.lastname: Trudeau
mesh_terms: D000818:Animals; D002864:Chromogranins; D005260:Female; D006054:Goldfish / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000502:physiology*; D013006:Growth Hormone / Q000235:genetics / Q000378:metabolism; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012474:Salmon; D012621:Seasons; D012737:Sex Factors; D013739:Testosterone / Q000494:pharmacology
chemical_list: D002864:Chromogranins; D012739:Gonadal Steroid Hormones; D037101:Luteinizing Hormone, beta Subunit; D011506:Proteins; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D013006:Growth Hormone