Lack of Effect of Synthetic Human Gastric Inhibitory Polypeptide and Glucagon-LikePeptide 1 [7-36 Amide] Infused at Near-Physiological Concentrations on Pentagastrin-Stimulated Gastric Acid Secretion in Normal Human Subjects

Gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 [7-36 amide] (GLP-1) are glucose-dependent insulinotropic gut hormones. Under experimental conditions, both have been shown to reduce stimulated gastric acid secretion. To study their individual and combined effects on pentagastrin-stimulated (0.1 μg/kg/h from – 90 to 120 min) gastric volume, acid and chloride output, on separate occasions, synthetic human GIP (1 pmol/kg/min) and/or GLP-1 [7-36 amide] (0.3 pmol/ kg/min) or placebo (0.9% NaCl with 1 % albumin) were infused intravenously (from – 30 to 120 min) in 9 healthy volunteers. At 0 min, a glucose infusion was started that mimicked the glycemic profile after an oral glucose load of 50 g/400 ml and allowed for the glucose-dependent insulinotropic action of GIP and GLP-1 [7-36 amide]. Pentagastrin stimulated acid output significantly, but neither GIP nor GLP-1 [7-36 amide] either alone or in combination, reduced pentagastrin-stimulated gastric acid secretion. The circulating concentrations of GIP and GLP-1 [7-36 amide] obtained at steady state during exogenous administration of synthetic peptides were similar to or higher than those reached after oral glucose (endogenous secretion). In conclusion, (penta) gastrin-stimulated gastric acid secretion is not inhibited by physiological circulating concentrations of GIP or GLP-1 [7-36 amide]. Therefore, the insulinotropic action of these intestinal hormones is physiologically more important than their possible role as enterogastrone.