Potentiation effect of cholecystokinin-octapeptide on pancreatic bicarbonate secretion stimulated by a physiologic dose of secretin in humans.

We studied the potentiation effect of cholecystokinin-octapeptide and secretin on pancreatic secretion of bicarbonate and trypsin in humans. The pancreatic bicarbonate and trypsin outputs were determined by using a triple-lumen duodenal tube and indicator dilution technique while gastric juice was completely aspirated. When cholecystokinin-octapeptide in varied doses, 2.6, 5.3, 10.9, 26.3, 52.6, and 109.4 pmol . kg-1 . h-1, was added to i.v. infusion of secretin in a physiologic dose, 0.03 clinical units (CU) . kg-1 . h-1, the bicarbonate outputs were significantly greater than those achieved by secretin or cholecystokinin-octapeptide alone or the sum of the bicarbonate outputs produced by each hormone. The potentiation effect of cholecystokinin-octapeptide occurred at the dose of 10.9 pmol . kg-1 . h-1. No further further augmentation on the bicarbonate output occurred when the dose of cholecystokinin-octapeptide was increased in the dose range greater than 10.9 pmol . mg-1 . h-1. No potentiation on pancreatic secretion of trypsin was apparent when the two hormones were given simultaneously. Thus, cholecystokinin-octapeptide in a relatively small dose range potentiated the pancreatic bicarbonate secretion stimulated by a physiologic dose of secretin. The pancreatic enzyme secretion does not appear to be potentiated by two hormones.