Elevation of plasma CCK concentration after intestinal administration of a pancreatic enzyme secretion-stimulating peptide purified from rat bile-pancreatic juice: analysis with N-terminal region specific radioimmunoassay.

The rat plasma cholecystokinin (CCK) concentration was measured after intestinal administration of a peptide purified from rat bile-pancreatic juice, which has a stimulatory effect on pancreatic enzyme secretion. The plasma CCK concentration was measured by means of a radioimmunoassay using CCK-8 N-terminal specific antibody, OAL-656. In experimental rats with protease-free intestines, intraduodenal infusion of 10 micrograms of the purified peptide, which stimulates pancreatic enzyme secretion 2.0-2.5 fold, induced a significant increase in the plasma CCK level. Furthermore, after removal of CCK from the plasma by immunoabsorption with an OAL-656-bound Sepharose 4B column, the stimulatory effect of the plasma on pancreatic enzyme secretion was abolished when it was injected intravenously into recipient rats. It was concluded that this peptide stimulates the release of CCK in the intestine and that this is responsible at least in part for the pancreatic enzyme secretion-stimulating activity of the peptide.