title: Influence of membrane ion channel in pituitary somatotrophs by hypothalamic regulators.
abstract: The secretion of growth hormone (GH) from somatotrophs located within the anterior pituitary gland is stimulated by endogenous hypothalamic growth hormone-releasing hormone (GHRH) and the GH secretagogue (GHS) ghrelin, and inhibited by somatotropin-releasing inhibitory factor (SRIF, also known as somatostatin). These factors bind to specific G-protein-coupled receptors on the cell membrane, and directly or indirectly modify the properties of ion channels and second messenger systems. Ultimately this results in a change in intracellular free Ca(2+) concentration ([Ca(2+)](i)) and the secretion of GH. Somatotrophs possess a variety of ion channels on their membranes, and modification of these ion channels, especially Ca(2+), K(+), and Na(+) channels, is tightly linked to intracellular Ca(2+) levels and therefore hormone secretion. Various issues regarding receptor distribution, role of ion channels, alteration of membrane potential, and involvement of intracellular signaling system in the control of GH secretion are discussed in this review. In particular, this work will focus on ion channels and [Ca(2+)](i) in somatotrophs.
authors.affiliation: School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia.
authors.forename: Seung-Kwon
authors.initials: SK
authors.lastname: Yang
authors.forename: Frederik
authors.initials: F
authors.lastname: Steyn
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
mesh_terms: D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D054439:Ghrelin / Q000378:metabolism; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D007031:Hypothalamus / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000378:metabolism; D013004:Somatostatin / Q000378:metabolism; D052683:Somatotrophs / Q000502:physiology*
chemical_list: D054439:Ghrelin; D007473:Ion Channels; D013004:Somatostatin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone