title: Three forms of GnRH in the brain and pituitary of the turbot, Scophthalmus maximus: immunological characterization and seasonal variation.
abstract: Three forms of GnRH, chicken (c) GnRH-II, salmon (s) and seabream (sb) GnRH, were immunologically characterized in the brain and pituitary of turbot by ELISA. cGnRH-II and sGnRH were detected in the brain, while sbGnRH and sGnRH (but not cGnRH-II) were detected in the pituitary. In females, the levels of cGnRH-II in the turbot brain extracts increased from May to July, concomitant with an increase in oocyte diameter. In the pituitary, sbGnRH was found to be the dominant form, with levels 100-600-fold those of sGnRH. Both sGnRH and sbGnRH in the pituitary showed variation during the spawning season; sbGnRH increased from May to July and correlated with the increase in oocyte diameter, while sGnRH decreased. The overall patterns were the same for male turbot, although levels were generally lower. These findings suggest that sbGnRH could be controlling reproduction in the turbot. However, the seasonal variation in sGnRH indicates a potential physiological role in turbot reproduction. This study gives the first immunological indications that sbGnRH is present in the pituitary of a pleuronectiform fish, and will provide the basis for further studies on the endocrine regulation of reproduction in flatfish.
authors.affiliation: Department of Fisheries and Marine Biology, University of Bergen, P.O. Box 7800, N-5020, Bergen, Norway. eva.andersson@ifm.uib.no
authors.forename: E
authors.initials: E
authors.lastname: Andersson
authors.forename: P G
authors.initials: PG
authors.lastname: Fjelldal
authors.forename: U
authors.initials: U
authors.lastname: Klenke
authors.forename: E
authors.initials: E
authors.lastname: Vikingstad
authors.forename: G L
authors.initials: GL
authors.lastname: Taranger
authors.forename: Y
authors.initials: Y
authors.lastname: Zohar
authors.forename: S O
authors.initials: SO
authors.lastname: Stefansson
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005412:Flatfishes / Q000378:metabolism* / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000276:immunology / Q000378:metabolism*; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*; D020033:Protein Isoforms / Q000276:immunology / Q000378:metabolism*; D012621:Seasons
chemical_list: D020033:Protein Isoforms; D007987:Gonadotropin-Releasing Hormone