Variable contribution of gastrin to gastric acid secretion after a meal in humans

The purpose of these experiments was to determine the contribution of gastrin to the acid secretory response to eating in healthy human subjects. To simulate the gastric and intestinal phases of eating, a meal was homogenized and then infused into the stomach through a nasogastric tube. At the same time, the cephalic phase of acid secretion was activated by sham feeding. With this simulated meal, mean serum gastrin concentration increased from a basal value of 43 +/- 9 pg/ml to an average postprandial gastrin concentration over 2 h of 121 +/- 25 pg/ml. Gastrin release after this simulated meal was similar to gastrin release after a normally eaten meal in the same 12 subjects. Gastric acid secretion in response to the simulated meal, which was measured by in vivo intragastric titration, averaged 24.2 +/- 2.4 mmol/h. To determine how much of this postprandial acid secretion could be attributed to gastrin, gastrin 17 I was infused intravenously in the same subjects on a separate day and acid secretion and serum gastrin concentrations were measured. By relating serum gastrin concentration during gastrin 17 infusion to concomitant acid secretion, we determined that an average postprandial serum gastrin concentration of 121 pg/ml could result in an acid secretion rate of 21.5 mmol/h, 89% of the actual acid secreted after the simulated meal in these subjects. However, in individual subjects, the amount of gastrin released after a meal could produce as little as 51% or as much as 162% of actual postprandial acid secretion. Thus, in individual human subjects the contribution of gastrin to acid secretion after a meal is variable.