title: Regulation of sex steroid production and mRNAs encoding gonadotropin receptors and steroidogenic proteins by gonadotropins, cyclic AMP and insulin-like growth factor-I in ovarian follicles of rainbow trout (Oncorhynchus mykiss) at two stages of vitellogenesis.
abstract: At the completion of vitellogenesis, the steroid biosynthetic pathway in teleost ovarian follicles switches from estradiol-17β (E2) to maturational progestin production, associated with decreased follicle stimulating hormone (Fsh) and increased luteinizing hormone (Lh) signaling. This study compared effects of gonadotropins, human insulin-like growth factor-I (IGF1), and cAMP/protein kinase A signaling (forskolin) on E2 production and levels of mRNAs encoding steroidogenic proteins and gonadotropin receptors using midvitellogenic (MV) and late/postvitellogenic (L/PV) ovarian follicles of rainbow trout. Fsh, Lh and forskolin, but not IGF1, increased testosterone and E2 production in MV and L/PV follicles. Fsh increased steroidogenic acute regulatory protein (star; MV), 3β-hydroxysteroid dehydrogenase/Δ(5-4) isomerase (hsd3b; MV) and P450 aromatase (cyp19a1a; MV) transcript levels. Lh increased star mRNA levels (MV, L/PV) but reduced cyp19a1a transcripts in L/PV follicles. At both follicle stages, IGF1 reduced levels of hsd3b transcripts. In MV follicles, IGF1 decreased P450 side-chain cleavage enzyme (cyp11a1) transcripts but increased cyp19a1a transcripts. In MV follicles only, forskolin increased star and hsd3b transcripts. Forskolin reduced MV follicle cyp11a1 transcripts and reduced cyp19a1a transcripts in follicles at both stages. Fsh and Lh reduced fshr transcripts in L/PV follicles. Lh also reduced lhcgr transcripts (L/PV). IGF1 had no effect on gonadotropin receptor transcripts. Forskolin reduced MV follicle fshr transcript levels and reduced lhcgr transcripts in L/PV follicles. These results reveal hormone- and stage-specific transcriptional regulation of steroidogenic protein and gonadotropin receptor genes and suggest that the steroidogenic shift at the completion of vitellogenesis involves loss of stimulatory effects of Fsh and Igfs on cyp19a1a expression and inhibition of cyp19a1a transcription by Lh.
authors.affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105, USA; Atmosphere and Ocean Research Institute, University of Tokyo, Chiba 277-8564, Japan.
authors.forename: Ikumi
authors.initials: I
authors.lastname: Nakamura
authors.affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105, USA; Atmosphere and Ocean Research Institute, University of Tokyo, Chiba 277-8564, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kusakabe
authors.affiliation: Northwest Fisheries Science Center, NOAA's National Marine Fisheries Service, Seattle, WA 98112, USA; Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA.
authors.forename: Penny
authors.initials: P
authors.lastname: Swanson
authors.affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105, USA; Center for Reproductive Biology, Washington State University, Pullman, WA 99164, USA. Electronic address: grahamy@u.washington.edu.
authors.forename: Graham
authors.initials: G
authors.lastname: Young
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004958:Estradiol / Q000096:biosynthesis; D005260:Female; D029941:Fish Proteins / Q000235:genetics*; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000502:physiology*; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics; D011375:Progesterone Reductase / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011967:Receptors, Gonadotropin / Q000235:genetics*; D013251:Steroid Isomerases / Q000235:genetics; D013739:Testosterone / Q000096:biosynthesis; D014818:Vitellogenesis / Q000235:genetics / Q000502:physiology; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: C021425:3 beta-hydroxysteroid oxidoreductase-delta(5) 3-ketosteroid isomerase; D029941:Fish Proteins; D012739:Gonadal Steroid Hormones; D009097:Multienzyme Complexes; D010750:Phosphoproteins; D012333:RNA, Messenger; D011967:Receptors, Gonadotropin; D000098682:Steroidogenic Acute Regulatory Protein; D005576:Colforsin; D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D000242:Cyclic AMP; D011375:Progesterone Reductase; D001141:Aromatase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D013251:Steroid Isomerases
keywords: Gonadotropin receptors; Gonadotropins; Insulin-like growth factor I; Ovarian follicle; Rainbow trout; Steroidogenesis