The negative feedback mechanism of gastric acid secretion: Significance of acid in the gastric juice in man and dog.

As reported previously, gastrin-stimulated gastric secretion in the dog and in man was suppressed by an intravenous infusion of secretin, These results, both in the dog and in man, also were obtained by introduction of acid into the duodenum, which indicated that both endogenous and exogenous secretion inhibit gastrin-stimulated gastric secretion at the oxyntic cell level. Feeding a test meal in man gave rise to an increase of plasma gastrin, reaching a peak of 120 pg. per milliliter at 15 minutes after feeding and remaining above control level for 2 to 3 hours. Is was found that plasma gastrin was suppressed greatly during the intravenous infusion of pure secretin. In animal experiments endogenous gastrin release produced by irrigation of the antral pouch also inhibited both endogenous and exogenous secretin. These results indicate that secretin inhibits gastrin release at the G-cell level in the antrum. On the other hand, it also was observed that endogenous gastrin release ceased when the pH of the perfusate dropped below 2.5. The following conclusions are drawn from the above findings. (1) Gastrin release is suppressed primarily by direct contact of acid with the antrum. The feedback mechanism in this case operates intraluminally in the stomach. (2) The low pH content of the stomach stimulates the release of secretin from the duodenum. The secretin released in this way not only inhibits gastric acid secretion at the oxyntic cell secretin released in this way not only inhibits gastric acid secretion at the oxyntic cell secretin released of gastrin at the G-cell level in the antrum. The level but also blocks the release of gastrin at the G-cell level in the antrum. The feedback mechanism brought about by acid of gastric origin occurs through the general circulation.