Ion channels and the signal transduction pathways in the regulation of growth hormone secretion.
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.
Chen
C
C
Prince Henry's Institute of Medical Research, Clayton, Victoria 3168, Australia.
Vincent
J D
JD
Clarke
I J
IJ