PACAP stimulation of maturational gonadotropin secretion in goldfish involves extracellular signal-regulated kinase, but not nitric oxide or guanylate cyclase, signaling.
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.
Chang
John P
JP
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada. john.chang@ualberta.ca
Sawisky
Grant R
GR
Mitchell
Gabriel
G
Uretsky
Aubrey D
AD
Kwong
Patrick
P
Grey
Caleb L
CL
Meints
Amanda N
AN
Booth
Morgan
M
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D003497:Cyclic N-Oxides / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006054:Goldfish; D006062:Gonadotropins / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics
D002070:Butadienes; D003497:Cyclic N-Oxides; D005419:Flavonoids; D016166:Free Radical Scavengers; D006062:Gonadotropins; D007093:Imidazoles; D020030:Nitric Oxide Donors; D009570:Nitriles; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; C113580:U 0126; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; D048049:Extracellular Signal-Regulated MAP Kinases; D006162:Guanylate Cyclase; D006152:Cyclic GMP; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one