Cholecystokinin 6 (CCK6)

Phospholipase C (PLC) inhibitor inhibited amylase secretion induced by high doses of CCK-6 and CCK-4 but not by CCK-5. Protein tyrosine kinase (PTK) inhibitor only inhibited the action of high doses of CCK-4. Neither PLC inhibitor nor PTK inhibitor affected amylase secretion evoked by low doses of CCK-6, CCK-5, and CCK-4. In contrast to its actions on JMV-180 and CCK-OPE, phospholipase A2 (PLA2) inhibitor had no effect on the action evoked by all CCK short peptides. CCK-6, CCK-5, and CCK-4 caused a 2.1- to 3.2-fold increase in intracellular inositol 1,4,5-trisphosphate levels over basal. None of these CCK short peptides increased intracellular arachidonic acid levels. CCK-6 and CCK-5 did not stimulate PTK activity, whereas CCK-4 evoked a 3.2- to 5.3-fold increase over basal.At low doses, CCK-6, CCK-5, and CCK-4 utilize some yet to be identified pathways to evoke Ca2+ oscillations and amylase secretion.