Cholecystokinin-evoked Ca2+ waves in isolated mouse pancreatic acinar cells are modulated by activation of cytosolic phospholipase A2, phospholipase D, and protein kinase C

We employed confocal laser-scanning microscopy to monitor cholecystokinin (CCK)-evoked Ca2+ signals in fluo-3-loaded mouse pancreatic acinar cells. CCK-8-induced Ca2+ signals start at the luminal cell pole and subsequently spread toward the basolateral membrane. Ca2+ waves elicited by stimulation of high-affinity CCK receptors (h.a.CCK-R) with 20 pM CCK-8 spread with a slower rate than those induced by activation of low-affinity CCK receptors (l.a.CCK-R) with 10 nM CCK-8. However, the magnitude of the initial Ca2+ release was the same at both CCK-8 concentrations, suggesting that the secondary Ca2+ release from intracellular stores is modulated by activation of different intracellular pathways in response to low and high CCK-8 concentrations. Our experiments suggest that the propagation of Ca2+ waves is modulated by protein kinase C (PKC) and arachidonic acid (AA). The data indicate that h.a.CCK-R are linked to phospholipase C (PLC) and phospholipase A, (PLA,) cascades, whereas l.a.CCK-R are coupled to PLC and phospholipase D (PLD) cascades. The products of PLA, and PLD activation, AA and diacylglycerol (DAG), cause inhibition of Ca2+ wave propagation by yet unknown mechanisms. (C) 1999 Academic Press.