Effects of gastric inhibitory polypeptide on dispersed pancreatic acinar cells from the guinea pig.

Purified natural porcine gastric inhibitory polypeptide (GIP), in high concentrations, was found to stimulate outflow of 45Ca, increase cellular accumulation of cyclic GMP and cyclic AMP and cause release of amylase from dispersed pancreatic acinar cells. Synthetic GIP increased cellular cyclic AMP levels, but did not affect outflux of calcium, cellular levels of cyclic GMP or release of amylase. The discrepancy between results with natural and synthetic preparations of porcine GIP may be explained by a possible contamination of natural GIP with cholecystokinin. Other examined pancreatic secretory stimulating peptides which induce cyclic AMP accumulation in acinar cells, also increase release of amylase. Synthetic GIP increased levels of cyclic AMP without affecting amylase release. This suggests that the correlation between amylase release and total cellular accumulation of cyclic AMP in response to GIP is not close.