title: Nitric oxide and guanylate cyclase signalling are differentially involved in gonadotrophin (LH) release responses to two endogenous GnRHs from goldfish pituitary cells.
abstract: Nitric oxide synthase (NOS) immunoreactivity is present in goldfish gonadotrophs. The present study investigated whether two native goldfish gonadotrophin-releasing hormones (GnRHs), salmon (s)GnRH and chicken (c)GnRH-II, use NOS/nitric oxide (NO) and soluble guanylate cyclase (sGC)/cyclic (c)GMP/protein kinase G (PKG) signalling to stimulate maturational gonadotrophin [teleost gonadotrophin-II, luteinising hormone (LH)] release. In cell column perifusion experiments with dispersed goldfish pituitary cells, the application of three NOS inhibitors (aminoguanidine hemisulphate, 1400W and 7-nitroindazole) and two NO scavengers [2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) and rutin hydrate] reduced sGnRH-elicited, but not cGnRH-II-induced, LH increases. The NO donor sodium nitroprusside (SNP) increased NO production in goldfish pituitary cells in static incubation. SNP-stimulated LH release in column perifusion was attenuated by PTIO and the sGC inhibitor 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-oneon (ODQ), and additive to responses elicited by cGnRH-II, but not sGnRH. ODQ and the PKG inhibitor KT5823 decreased sGnRH- and cGnRH-II-stimulated LH release. Similarly, the LH response to dibutyryl cGMP was reduced by KT5823. These results indicate that, although only sGnRH uses the NOS/NO pathway to stimulate LH release, both GnRHs utilise sGC/PKG to increase LH secretion.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
authors.forename: A N
authors.initials: AN
authors.lastname: Meints
authors.forename: J G
authors.initials: JG
authors.lastname: Pemberton
authors.forename: J P
authors.initials: JP
authors.lastname: Chang
mesh_terms: D000818:Animals; D002227:Carbazoles / Q000494:pharmacology; D005260:Female; D006054:Goldfish; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010902:Pituitary Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction
chemical_list: D002227:Carbazoles; D020030:Nitric Oxide Donors; D047428:Protein Kinase Inhibitors; C073601:KT 5823; D009599:Nitroprusside; D009569:Nitric Oxide; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D006162:Guanylate Cyclase