Duodenal acidification releases cholecystokinin.

We studied the effect of hydrochloric acid (HCl) in the proximal small intestine on release of cholecystokinin (CCK) and secretin and on exocrine pancreatic secretion in conscious dogs with gastric cannulas and modified Herrera pancreatic cannulas. Intraduodenal administration of HCl in a concentration of 50 or 100 mM at rates of 0.05, 0.1, 0.2, and 0.4 mmol/min significantly increased plasma concentration of CCK in a dose-dependent manner, whereas plasma gastrin levels decreased. The increased plasma CCK level paralleled a significant increase in pancreatic trypsin output. Plasma secretin concentration and pancreatic bicarbonate output also increased in response to the acid, and the increase was dependent on the acid loads delivered in the duodenum. Thus, in dogs, HCl in the duodenum releases both CCK and secretin to stimulate pancreatic secretion of bicarbonate as well as enzymes.