title: Electrophysiological differences between fshb- and lhb-expressing gonadotropes in primary culture.
abstract: Synthesis and release of FSH and LH are differentially regulated by GnRH, but the mechanisms by which this regulation is achieved are not well understood. Teleost fish are powerful models for studying this differential regulation because they have distinct pituitary cells producing either FSH or LH. By using pituitary cultures from Atlantic cod (Gadus morhua), we were able to investigate and compare the electrophysiological properties of fshb- and lhb-expressing cells, identified by single-cell quantitative PCR after recording. Both cell types fired action potentials spontaneously. The relative number of excitable cells was dependent on reproductive season but varied in opposing directions according to season in the 2 cell types. Excitable and quiescent gonadotropes displayed different ion channel repertoires. The dynamics of outward currents and GnRH-induced membrane responses differed between fshb- and lhb-expressing cells, whereas GnRH-induced cytosolic Ca²⁺ responses were similar. Expression of Ca²⁺-activated K⁺ channels also differed with cell type and showed seasonal variation when measured in whole pituitary. The differential presence of these channels corresponds to the differences observed in membrane response to GnRH. We speculate that differences in ion channel expression levels may be involved in seasonal regulation of hormone secretion as well as the differential response to GnRH in LH- and FSH-producing gonadotropes, through differences in excitability and Ca²⁺ influx.
authors.affiliation: Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, N-0033 Oslo, Norway.
authors.forename: Kjetil
authors.initials: K
authors.lastname: Hodne
authors.forename: Rønnaug A U
authors.initials: RA
authors.lastname: Strandabø
authors.forename: Kristine
authors.initials: K
authors.lastname: von Krogh
authors.forename: Rasoul
authors.initials: R
authors.lastname: Nourizadeh-Lillabadi
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: D000818:Animals; D001267:Atlantic Ocean; D020013:Calcium Signaling; D002478:Cells, Cultured; D055724:Electrophysiological Phenomena; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism*; D048389:Gadus morhua / Q000254:growth & development / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D052681:Gonadotrophs / Q000166:cytology / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009664:Norway; D010902:Pituitary Gland / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D024681:Potassium Channels, Calcium-Activated / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D055703:Reproductive Physiological Phenomena; D012621:Seasons
chemical_list: D029941:Fish Proteins; D037201:Follicle Stimulating Hormone, beta Subunit; D037101:Luteinizing Hormone, beta Subunit; D024681:Potassium Channels, Calcium-Activated; D020033:Protein Isoforms; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone