Signal Transduction Pathways in GnRH- and Dopamine D1-Stimulated Growth Hormone Secretion in the Goldfish

John P. Chang ； Fredrick Van Goor ； Anderson O. L. Wong ； Richard M. Jobin ； Catherine M. Neumann

《The Chinese Journal of Physiology》 37卷3期 (1994/09) Pp. 111-127

並列摘要

In goldfish, growth hormone (GH) secretion is regulated by multiple neuroendocrine factors. Among these regulators, gonadotropin-releasing hormone (GnRH) and dopamine (DA) are efiective stimulators of GH release. The stimulatory actions of GnRH and DA are mediated by GnRH and DA D1 receptors on somatotropes, respectively. In this article, results from recent in vitro pharmacologlcal and electrophysiological studies examining the possible involvementof extracellular Ca(superscript 2+), protein kinase C, voltage-sensitive Ca(superscript 2+) channels (VSCC) and phospholipase A2 in mediating GnRH-induced GII release are presented. Results from experiments investigating the possible interactions of cyelic adenosine 3'5'-monophosphate (cAMP), and extracellular Ca(superscript 2+) entry through VSCC in mediating the DA Di-elicited GH response are also reported. These data were discussed in conjunction with other information available in the literature on the signal transduction mechanisms mediating GH secretion in goldfish. Based on these findings, a model for the transduction pathways integrating the initiation and maintenance of the distinct GnRH-induced and DA D1-clicitcd GH responses was proposed. GnRH and DA stimulate GH release via separate PKC- and cAMP-dependent mechanisms, respectively. These signalling mechanisms appear to act on distinct GH pools. PKC and cAMP subsequently activate VSCC. Ca(superscript 2+) entry through VSCC plays a role in the sustained GH release response by enhancing the PKC- and cAMP-induced GH release.

並列關鍵字

dispered soldfish pituitary cells ； second messengers ； GH release ； voltage-Sensitive Ca(superscript 2+)channels ； protein kinase C ； cAMP ； calcium currents ； phospholipase A2•