title: Ion channels and the signal transduction pathways in the regulation of growth hormone secretion.
abstract: The secretion of GH from pituitary somatotrophs is mainly regulated by alterations in the levels of intracellular free Ca(2+) concentrations ([Ca(2+)](i)) that depend on the influx of Ca(2+) through voltage-gated Ca(2+) channels in the cell membrane. Hypothalamic stimulatory and inhibitory factors bind to specific receptors on the cell membrane to regulate membrane potential and activate second-messenger systems. The receptors are G-protein coupled, and activated G proteins directly influence membrane ion channels to regulate Ca(2+) influx. The function of cAMP-dependent protein kinase A is also modulated by receptor-coupled G proteins leading to the phosphorylation of Ca(2+) channel proteins and further alteration of Ca(2+) influx.
authors.affiliation: Prince Henry's Institute of Medical Research, Clayton, Victoria 3168, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: J D
authors.initials: JD
authors.lastname: Vincent
authors.forename: I J
authors.initials: IJ
authors.lastname: Clarke