Role of Ca2+ stores in dopamine- and PACAP-evoked growth hormone release in goldfish.
Growth hormone (GH) secretion, evoked by either pituitary adenylate cyclase-activating polypeptide (PACAP) or dopamine (DA), is dependent on both voltage-sensitive calcium channels (VSCC) and cAMP signaling in goldfish. We further characterized the involvement of Ca2+ in evoked release by PACAP and DA, by examining the sensitivity of evoked GH release to perturbations of Ca2+ signaling. Both VSCC and calmodulin/calmodulin-dependent kinase are involved in PACAP signaling as had been shown for DA. In spite of this apparent dependence on VSCC, blockade of TMB-8 but not ryanodine-sensitive intracellular Ca2+ stores inhibited both PACAP- and DA-evoked GH release. Using sarcoplasmic/endoplasmic reticulum Ca-ATPases (SERCA) inhibitors, we found BHQ blocked, whereas thapsigargin (Tg) enhanced stimulated GH release, suggesting that Tg-sensitive SERCA may counteract these cAMP-mobilizing neuroendocrine regulators by sequestering [Ca2+]i. As GH secretion stimulated by two endogenous gonadotropin-releasing hormones is not affected by Tg, it appears that distinct multiple Ca2+ stores mediate the hormone releasing response to different neuroendocrine regulators.
Chang
J P
JP
Department of Biological Sciences, University of Alberta, CW 405, Biological Sciences Building, Edmonton, Alta, Canada T6G 2E9. john.chang@ualberta.ca
Wong
C J H
CJ
Davis
P J
PJ
Soetaert
B
B
Fedorow
C
C
Sawisky
G
G
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000502:physiology; D002147:Calmodulin / Q000502:physiology; D004298:Dopamine / Q000494:pharmacology*; D006054:Goldfish; D013006:Growth Hormone / Q000378:metabolism*; D009479:Neuropeptides / Q000494:pharmacology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012433:Ryanodine / Q000494:pharmacology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors
D020746:Calcium Channels, L-Type; D002147:Calmodulin; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012433:Ryanodine; D019284:Thapsigargin; D013006:Growth Hormone; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; D004298:Dopamine