Atropine abolishes the potentiation effect of secretin and cholecystokinin-octapeptide on exocrine pancreatic secretion in humans.

Potentiating action between secretin and cholecystokinin on exocrine pancreatic secretion of bicarbonate has been well recognized. In the present study, we studied the effect of atropine on potentiating action on pancreatic exocrine secretion stimulated by exogenous secretin in physiologic dose and cholecystokinin-octapeptide in humans. Using a dye-dilution technique and a duodenal triple-lumen tube, pancreatic secretion of both bicarbonate and trypsin was determined while gastric juice was completely aspirated. Secretin given i.v. in a dose of 2.7 pmol/kg/h, which was known to achieve a similar plasma concentration of secretin after meal in humans, and cholecystokinin-octapeptide 26.2 pmol/kg/h potentiated pancreatic secretion of bicarbonate but not the pancreatic trypsin output. Atropine given i.v. in a dose of 1 mg/h abolished the potentiation effect of the two hormones on pancreatic bicarbonate output. Since the inhibitory effect of atropine on the secretin-stimulated bicarbonate output was statistically significant, the major inhibitory effect of atropine on the potentiation of pancreatic bicarbonate secretion appears to be its effect on the action of secretin.