title: Signal transduction involved in GnRH2-stimulation of identified LH-producing gonadotropes from lhb-GFP transgenic medaka (Oryzias latipes).
abstract: We have characterized the response to gonadotropin-releasing hormone 2 (GnRH2) in luteinizing hormone producing cells from gfp-transgenic medaka. Teleosts have separate cells producing the two types of gonadotropins, enabling us for the first time to study the intracellular signaling that controls secretion of each gonadotropin separately. Pituitary cell cultures were prepared, and lhb-producing cells were selected by their GFP expression. Cytosolic Ca(2+) imaging revealed three response patterns to GnRH2, one monophasic and two types of biphasic patterns. The Ca(2+) sources were examined by depleting intracellular Ca(2+) stores and preventing influx of extracellular Ca(2+). Both treatments reduced response amplitude, and affected latency and time to peak. Blocking L-type Ca(2+) channels reduced amplitude and time to peak, but did not remove extracellular Ca(2+) contribution. Patch-clamp recordings showed spontaneous action potentials in several cells, and GnRH2 increased the firing frequency. Presence of Ca(2+)-activated K(+) channels was revealed, BK channels being the most prominent.
authors.affiliation: University of Oslo, Department of Biosciences, Oslo, Norway. ronnaug.strandabo@imbv.uio.no
authors.forename: Rønnaug A U
authors.initials: RA
authors.lastname: Strandabø
authors.forename: Kjetil
authors.initials: K
authors.lastname: Hodne
authors.forename: Eirill
authors.initials: E
authors.lastname: Ager-Wick
authors.forename: Olav
authors.initials: O
authors.lastname: Sand
authors.forename: Finn-Arne
authors.initials: FA
authors.lastname: Weltzien
authors.forename: Trude M
authors.initials: TM
authors.lastname: Haug
mesh_terms: D000200:Action Potentials; D000818:Animals; D030801:Animals, Genetically Modified; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D020013:Calcium Signaling; D002478:Cells, Cultured; D005260:Female; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D015759:Ionomycin / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics* / Q000378:metabolism; D009990:Oryzias / Q000235:genetics* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D061251:Primary Cell Culture; D011401:Promoter Regions, Genetic; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D061207:Calcium Ionophores; D029941:Fish Proteins; D051036:Large-Conductance Calcium-Activated Potassium Channels; D037101:Luteinizing Hormone, beta Subunit; D049452:Green Fluorescent Proteins; D007987:Gonadotropin-Releasing Hormone; D015759:Ionomycin; D014700:Verapamil