CCKB receptor stimulation mediates [Ca2+]i increase but no PKC activation in Jurkat T-cells

Abstract

We have investigated the effect of cholecystokinin-octa- peptide (CCK-8) on [Ca²⁺]_i and protein kinase C (PKC) activity in Jurkat T-cells. CCK-8 produced a transient [Ca²⁺]_i increase in the presence of extracellular Ca²⁺. While CCK_B receptor antagonist L-365,260 abolished the elevation of [Ca²⁺]_i, CCK_A receptor antagonist L-364,718 was without effect. Moreover, the dihydropyridine calcium channel blocker nitrendipine was shown to block the observed calcium response. Results suggest that the calcium effect is caused by an interaction of CCK-8 with CCK_B binding sites and an influx of external Ca²⁺ via dihydropyridine sensitive calcium channels might serve as a source for the increased [Ca²⁺]_i. Because CCK-8 induced no PKC activation CCK_B receptor mediated rise of intracellular calcium seems not to include activation of phospholipase C.