The in Vitro Regulation of Growth Hormone Secretion by Orexins

Chen Chen and Xu, Ruwei (2003) The in Vitro Regulation of Growth Hormone Secretion by Orexins. Endocrine, 22 1: 57-66. doi:10.1385/ENDO:22:1:57

Author Chen Chen
Xu, Ruwei
Title The in Vitro Regulation of Growth Hormone Secretion by Orexins
Journal name Endocrine   Check publisher's open access policy
ISSN 0969-711X
Publication date 2003-10
Year available 2003
Sub-type Article (original research)
DOI 10.1385/ENDO:22:1:57
Volume 22
Issue 1
Start page 57
End page 66
Total pages 10
Editor P. M. Conn
Place of publication Totowa, N. J.
Publisher Humana Press
Language eng
Subject 110306 Endocrinology
110201 Cardiology (incl. Cardiovascular Diseases)
111201 Cancer Cell Biology
Abstract Orexins, orexigenic neuropeptides, have recently been discovered in lateral hypothalamus and play an important role in the regulation of pituitary hormone secretion. Two subtypes of orexin receptors (orexin-1 and orexin-2) have been demonstrated in pituitaries. In this experiment, the effects of orexins on voltage-gated Ca2+ currents and the GH release in primary cultured ovine somatotropes were examined. Voltage-gated Ca2+ currents were isolated in ovine somatotropes as L, T, and N currents using whole-cell patch-clamp techniques and specific Ca2+ channel blocker and toxin. Application of orexin-A or orexin-B (100 nM) significantly, dose-depen-dently, and reversibly increased only nifedipine-sensitive L-type Ca2+ current. Inhibitors of PKC (calphostin C, PKC inhibitory peptide) but not inhibitors of PKA (H89, PKA inhibitory peptide) cancelled the increase in the L current by orexins. Co-administration of orexin-A and GHRH (10 nM) showed an additive effect on the L current. Specific intracellular Ca2+-store-depleting reagent, thapsigargin (1 µM), did not affect the orexin-induced increase in the L current. Orexin-B alone slightly increased GH release and co-administration of orexin-A and GHRH synergistically stimulated GH secretion in vitro. It is therefore suggested that orexins may play an important role in regulating GHRH-stimulated GH secretion through an increase in the L-type Ca2+ current and the PKC-mediated signaling pathways in ovine somatotropes.
Keyword Orexins
Endocrine glands
Endocrine Diseases
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Biomedical Sciences Publications
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Created: Tue, 13 Jan 2009, 10:48:59 EST by Ms Karen Naughton on behalf of Institute for Molecular Bioscience