Gut hormones in stimulation of gastroduodenal alkaline secretion in conscious dogs

Alkaline secretion from the fundic and antral pouches of the stomach and the loops of proximal and distal duodenum was measured in conscious dogs under basal conditions and after intragastric instillation of HCl solution, meat feeding, or intravenous infusion of various gut hormones. In control tests on fasted dogs HCO-3 output from the duodenal mucosa was severalfold higher than that from the gastric mucosa. Instillation of 10 mM HCl into the stomach resulted in a significant increment in HCO-3 secretion from the gastric pouches and proximal duodenal loops, and this was accompanied by a marked increase in plasma secretin, cholecystokinin (CCK), and pancreatic polypeptide (PP) levels. Meat feeding stimulated HCO-3 secretion from proximal duodenum, and it was accompanied by a significant elevation in plasma gastrin, secretin, CCK, gastric inhibitory peptide, and PP. Among exogenous hormones, the most effective stimulant of HCO-3 secretion was PP, which caused a significant increase in HCO-3 output from the gastric and duodenal mucosa at doses (125-500 pmol X kg-1 X h-1) that raised plasma PP to postprandial levels. CCK in physiological doses (21-85 pmol.kg-.h-1) also stimulated HCO-3 secretion from gastric pouches and proximal duodenal loops. Neurotensin stimulated HCO-3 secretion from both gastric pouches and duodenal loops. In contrast, gastrin or secretin did not affect significantly HCO-3 secretion from the gastroduodenal mucosa. This study provides evidence that some gut hormones, particularly PP, CCK, and neurotensin, may be involved in the physiological stimulation of gastroduodenal alkaline secretion.