ROLE OF CHOLECYSTOKININ IN THE INHIBITION OF GASTRIC-ACID SECRETION IN DOGS

1. This study was designed to determine the involvement of cholecystokinin (CCK) in the gastric secretory responses to exogenous and endogenous secretagogues in conscious dogs with chronic gastric fistulae (GF), pancreatic fistulae (PF) and Heidenhain pouches (HP). 2. A meal of meat or intragastric application of peptone (300 mosm) increased secretion of HCI from the HP and pancreatic secretion of protein and plasma levels of gastrin, CCK and somatostatin. 3. The CCK receptor antagonist L-364,718 caused a further increase in the postprandial HCl secretion from the HP and in the plasma levels of gastrin and CCK but pancreatic output of protein and plasma concentration of somatostatin were significantly reduced. 4. Addition to intragastric peptone of 10% oleate or its acidification to pH 3.0 profoundly inhibited the HP secretion and gastrin release but significantly increased pancreatic secretion of protein and plasma levels of CCK and somatostatin. Administration of L-364,718 reversed the fall in the HP secretion and plasma gastrin while significantly attenuating pancreatic protein secretion and plasma somatostatin levels. 5. Intragastric administration of hyperosmolar (1200 mosm) peptone also inhibited HCI secretion from the HP but this was not affected by L-364,718. 6. Exogenous CCK and bombesin (but not gastrin) caused a small increase in HCI secretion from the HP and marked stimulation of pancreatic protein secretion accompanied by a significant rise in plasma levels of gastrin, CCK and somatostatin. Administration of L-364,718 resulted in a further increase in the HCI response of HP to bombesin and in plasma levels of gastrin and CCK but caused a reduction in plasma levels of somatostatin. 7. We conclude that CCK released by a meal of meat, intragastric peptone, oleate or acidified peptone and intravenous bombesin exerts tonic inhibitory influences on gastric acid secretion and that this effect is mediated, at least in part, by somatostatin.