Hormonal mechanism of sodium oleate-stimulated pancreatic secretion in rats

We have investigated the role of two intestinal hormones, secretin and cholecystokinin (CCK), on the pancreatic exocrine secretion stimulated by sodium oleate in anesthetized rats. Each rat was prepared with a polyethylene tube in the proximal duodenum and ligation of the pylorus. To collect pancreatic juice, the common bile-pancreatic duct was cannulated near the duodenal wall while bile was diverted to the exterior. Intraduodenal infusion of sodium oleate at doses of 0.03, 0.06, 0.12, and 0.24 mmol/h resulted in significant increases in pancreatic secretion including fluid, bicarbonate, and protein output. The increases of the three parameters were dose dependent and were correlated well with the increases in plasma secretin and CCK concentrations. To further clarify their hormonal roles, we have repeated identical experiments under intravenous administration of a rabbit anti-secretin serum (0.1 ml) or CR 1409 (4 mg.kg-1.h-1), a CCK-receptor antagonist, or a combination of both the antiserum and CR 1409. The antiserum significantly suppressed volume flow and bicarbonate secretion with a minor inhibitory effect on protein secretion, whereas a normal rabbit serum did not. CR 1409 significantly suppressed all three parameters. The combined treatment with both the antiserum and CR 1409 almost completely abolished the pancreatic secretion. Atropine given intravenously significantly inhibited the protein output but did not influence volume flow or bicarbonate output in response to sodium oleate. We thus conclude that, in rats, fat-stimulated pancreatic secretion of volume flow and bicarbonate depends entirely on the circulating endogenous secretin and CCK but that the protein output appears to be under control of both hormonal and cholinergic controls.