Gastric acid regulates the release of plasma secretin in man

Abstract

Fasting plasma secretin determined in 9 healthy subjects, 12 patients with active duodenal ulcer and 4 with Zollinger-Ellison syndrome were 3.2 .+-. 0.4, 5.1 .+-. 1.2 and 20.3 .+-. 1.3 pmol/l, respectively, (mean .+-. SEM [standard error of the mean]). Cimetidine significantly (P < 0.05) reduced levels in those with duodenal ulcer, as did gastric aspiration in the Zollinger-Ellison group. A significant correlation (P < 0.001) was found between basal acid output and mean fasting plasma secretin. After a solid meal and subsequent liquid soft drink, no sustained mean rise in plasma secretin was observed; changes in secretin appeared to coincide in time with rapid falls in duodenal pH, though little relationship could be established between the absolute level of pH and changes in plasma secretin. The mean peak postprandial rise in plasma secretin observed after solids was significantly (P < 0.05) greater in duodenal ulcer patients than controls (9.1 .+-. 1.1 vs. 6.7 .+-. 0.5 pmol/l) as was the mean integrated postprandial release (1002 .+-. 110 vs. 710 .+-. 67 pmol min-1 l-1). Cimetidine reduced both rises (P < 0.05) and was associated with significantly less duodenal pH readings below 4 (P < 0.001). Gastric acid is probably a major release mechanism for plasma secretin both fasting and after meal, but it is likely the acid load rather than absolute pH in the duodenum which determines circulating levels.