PACAP stimulation of maturational gonadotropin secretion in goldfish involves extracellular signal-regulated kinase, but not nitric oxide or guanylate cyclase, signaling

• Published in: General and comparative endocrinology 2010-01, Vol.165 (1), p.127-135
• Main Authors: Chang, John P, Sawisky, Grant R, Mitchell, Gabriel, Uretsky, Aubrey D, Kwong, Patrick, Grey, Caleb L, Meints, Amanda N, Booth, Morgan
• Format: Article
• Language: English
• Subjects: Animals; Butadienes - pharmacology; Carassius auratus; Cells, Cultured; cGMP and guanylate cyclase; Cyclic GMP - metabolism; Cyclic N-Oxides - pharmacology; Endocrinology & Metabolism; Extracellular Signal-Regulated MAP Kinases - antagonists & inhibitors; Extracellular Signal-Regulated MAP Kinases - physiology; Female; Flavonoids - pharmacology; Free Radical Scavengers - pharmacology; Freshwater; Goldfish; Gonadotropins - metabolism; Gonadotropins - secretion; Guanylate Cyclase - antagonists & inhibitors; Guanylate Cyclase - physiology; Imidazoles - pharmacology; Male; MEK; Nitric Oxide - metabolism; Nitric Oxide - physiology; Nitric Oxide Donors - pharmacology; Nitric oxide synthase; Nitriles - pharmacology; NO donors and scavengers; Pituitary Adenylate Cyclase-Activating Polypeptide - pharmacology; Pituitary Gland - cytology; Primary culture of dispersed pituitary cells; Signal Transduction - drug effects; Signal Transduction - genetics
• ISSN: 0016-6480; 1095-6840
• DOI: 10.1016/j.ygcen.2009.06.011

Abstract In goldfish, nitric oxide synthase (NOS) immunoreactivity is present in gonadotropes and extracellular signal-regulated protein kinase (ERK) mediates GnRH stimulation of gonadotropin release and synthesis. In this study, we tested the possible involvement of nitric oxide (NO) and ERK in mediating PACAP-stimulated maturational gonadotropin (GTH-II) release from primary cultures of dispersed goldfish pituitary cells. In static incubation experiments, PACAP-induced GTH-II release was unaffected by two inhibitors of NOS synthase, AGH and 1400W; whereas addition of a NO donor, SNAP, elevated GTH-II secretion. In perifusion experiments, neither NOS inhibitors (AGH, 1400W and 7-Ni) nor NO scavengers (PTIO and rutin hydrate) attenuated the GTH-II response to pulse applications of PACAP. In addition, the GTH-II responses to PACAP and the NO donor SNP were additive while PTIO blocked SNP action. Although dibutyryl cGMP increased GTH-II secretion in static incubation, inhibition of guanylate cyclase (GC), a known down-stream target for NO signaling, did not reduce the GTH-II response to pulse application of PACAP. On the other hand, GTH-II responses to PACAP in perifusion were attenuated in the presence of two inhibitors of ERK kinase (MEK), U 0126 and PD 98059. These results suggest that although increased availability of NO and cGMP can lead to increased GTH-II secretion, MEK/ERK signaling, rather than NOS/NO/GC activation, mediates PACAP action on GTH-II release in goldfish.