title: Molecular mechanisms of pituitary endocrine cell calcium handling.
abstract: Endocrine pituitary cells express numerous voltage-gated Na(+), Ca(2+), K(+), and Cl(-) channels and several ligand-gated channels, and they fire action potentials spontaneously. Depending on the cell type, this electrical activity can generate localized or global Ca(2+) signals, the latter reaching the threshold for stimulus-secretion coupling. These cells also express numerous G-protein-coupled receptors, which can stimulate or silence electrical activity and Ca(2+) influx through voltage-gated Ca(2+) channels and hormone release. Receptors positively coupled to the adenylyl cyclase signaling pathway stimulate electrical activity with cAMP, which activates hyperpolarization-activated cyclic nucleotide-regulated channels directly, or by cAMP-dependent kinase-mediated phosphorylation of K(+), Na(+), Ca(2+), and/or non-selective cation-conducting channels. Receptors that are negatively coupled to adenylyl cyclase signaling pathways inhibit spontaneous electrical activity and accompanied Ca(2+) transients predominantly through the activation of inwardly rectifying K(+) channels and the inhibition of voltage-gated Ca(2+) channels. The Ca(2+)-mobilizing receptors activate inositol trisphosphate-gated Ca(2+) channels in the endoplasmic reticulum, leading to Ca(2+) release in an oscillatory or non-oscillatory manner, depending on the cell type. This Ca(2+) release causes a cell type-specific modulation of electrical activity and intracellular Ca(2+) handling.
authors.affiliation: Section on Cellular Signaling, Program in Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, MD 20892-4510, United States. stankos@helix.nih.gov
authors.forename: Stanko S
authors.initials: SS
authors.lastname: Stojilkovic
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism*; D055098:Endocrine Cells / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D043562:Receptors, G-Protein-Coupled; D002118:Calcium