Characterization of Rat Lacrimal Gland Protein Kinase C: Effects of Phorbol Esters and PKC Inhibitors on Histone Kinase Activity and Labelled Protein Discharge
In the rat lacrimal gland, cholinergic agonists induce a large protein secretion through muscarinic receptors. The activation of these receptors stimulates phospholipase C that hydrolyses phosphatidylinositol 4,5-bisphosphate producing inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). The roles of IP3 and DAG as second messengers are now well documented. IP3 releases calcium from a non mitochondrial intracellular store which increases the cytosolic free calcium concentration. The released calcium may stimulate secretion directly, or may act with calmodulin to activate specific kinases that phosphorylate specific proteins to induce secretion. DAG activates protein kinase C (PKC), a calcium and phospholipid-dependent protein kinase, which also may phosphorylates specific proteins to evoke secretion.
KeywordsPhorbol Ester Lacrimal Gland Krebs Ringer Bicarbonate Buffer Cytosolic Free Calcium Concentration DE52 Column
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