Cholecystokinin and insulin regulate insulin-like growth factor II binding to pancreatic receptors; evidence of a role for intracellular calcium.

The binding of 125I-labeled insulin-like growth factor II (125I-IGF II) to mouse pancreatic acini was stimulated (45%) by insulin and inhibited (30%) by cholecystokinin octapeptide (CCK8). When CCK8 and insulin were added together, the effect on IGF II binding was similar to that seen when CCK8 was added alone. Two lines of evidence suggest that this effect of cholecystokinin on basal and insulin-stimulated 125I-IGF II binding was mediated via a change in intracellular calcium: (1) the cholinergic agent carbachol inhibited IGF II binding to its receptors; (2) addition of the Ca2+ ionophore A23187 mimicked the effects of CCK8 and carbachol. In contrast to its effects on IGF II binding to acini, CCK8 had only small effects on IGF I binding and no effects on insulin binding.