title: Seasonal effects of GnIH on basal and GnRH-induced goldfish somatotrope functions.
abstract: To understand how gonadotropin-inhibitory hormone (GnIH) regulates goldfish GH cell functions, we monitored GH release and expression during early, mid-, and/or late gonadal recrudescence. In vivo and in vitro responses to goldfish (g) GnIH were different, indicating direct action at the level of pituitary, as well as interactions with other neuroendocrine factors involved in GH regulation. Injection of gGnIH consistently reduced basal serum GH levels but elevated pituitary gh mRNA levels, indicating potential dissociation of GH release and synthesis. Goldfish GnRH (sGnRH and cGnRHII) injection differentially stimulated serum GH and pituitary gh mRNA levels with some seasonal differences; these responses were reduced by gGnIH. In contrast, in vitro application of gGnIH during 24-h static incubation of goldfish pituitary cells generally elevated basal GH release and attenuated sGnRH-induced changes in gh mRNA, while suppressing basal gh mRNA levels at mid- and late recrudescence but elevating them at early recrudescence. gGnIH attenuated the GH release responses to sGnRH during static incubation at early, but not at mid- and late recrudescence. In cell column perifusion experiments examining short-term GH release, gGnIH reduced the cGnRHII- and sGnRH-stimulated secretion at late recrudescence but inhibited tha action of cGnRHII only during mid-recrudescence. Interestingly, a reduction of basal GH release upon perifusion with gGnIH during late recrudescence was followed by a rebound increase in GH release upon gGnIH removal. These results indicate that gGnIH exerts complex effects on basal and GnRH-stimulated goldfish GH cell functions and can differentially affect GH release and mRNA expression in a seasonal reproductive manner.
authors.affiliation: Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: M
authors.initials: M
authors.lastname: Moussavi
authors.affiliation: Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9 Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: M
authors.initials: M
authors.lastname: Wlasichuk
authors.affiliation: Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9 Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: J P
authors.initials: JP
authors.lastname: Chang
authors.affiliation: Department of Biological SciencesUniversity of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4Department of Biological SciencesUniversity of Alberta, Edmonton, Alberta, Canada T6G 2E9 Habibi@ucalgary.ca.
authors.forename: H R
authors.initials: HR
authors.lastname: Habibi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006054:Goldfish / Q000097:blood / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D013006:Growth Hormone / Q000235:genetics / Q000378:metabolism; D007028:Hypothalamic Hormones / Q000494:pharmacology*; D008297:Male; D061251:Primary Cell Culture; D012621:Seasons; D052683:Somatotrophs / Q000187:drug effects* / Q000502:physiology
chemical_list: D007028:Hypothalamic Hormones; D007987:Gonadotropin-Releasing Hormone; D013006:Growth Hormone
keywords: gonadotropin-inhibitory hormone and RF amides; seasonality; serum GH; somatotropin production and secretion