The Inositol Phosphate-Calcium Signalling System in Lacrimal Gland Cells
In lacrimal gland cells, receptor-activated Ca2+ mobilization involves two phases: 1) Ca2+ release from an intracellular store, and 2) a more prolonged phase of extracellular Ca2+ entry (Parod and Putney, 1978; Putney, 1987). These two phases of the Ca2+ response can be dissected by stimulating cells with a phospholipase C-linked agonist in the presence or absence of extracellular Ca2+. In the absence of extracellular Ca2+, such stimulation results in a transient increase in Ca2+, originating from the release of a finite intracellular Ca2+ pool. In the presence of physiological (mM) extracellular Ca2+, the elevation in [Ca2+]i is sustained due to the additional component of extracellular Ca2+ influx. Extracellular Ca2+ influx is also the source for refilling of the intracellular Ca2+ pool upon termination of receptor activation.
KeywordsPermeability Ruthenium Inositol Saponin Phorbol
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