Characteristics of gastric inhibition by acidification of oxyntic gland area.

1. Gastric acid responses to the test meals were measured in the Heidenhain pouch, gastric and pancreatic fistula dogs, using the intragastric titration method, and monitoring the rate at which a solution of 1-0 N-NaOH had to be added to maintain the pH of the gastric content constant at pre-selected values ranging from 5-0 to 1-0. In this way the pH profile of the gastric acid and pepsin responses to a liver extract meal kept in the Heidenhain pouch or gastric fistula as well as to exogenous stimuli such as histamine, pentagastrin or Urecholine could be determined. 2. A liver extract meal adjusted to pH 5-0 produced a potent and pressure-related stimulation of acid secretion from the Heidenhain pouch without any change in secretion from the main stomach and pancreas or in the serum concentration of immuno-assayable gastrin. 3. Graded decrease of the liver extract meal pH to below 5-0 resulted in the pH-dependent inhibition of gastric acid output, which at pH 1-0 was only about 30% of the value attained at pH 5-0. Acid secretion from the Heidenhain pouch induced by exogenous stimuli such as histamine, pentagastrin or Urecholine also showed gradual decrease when the pH of the pouch content was decreased in sequential order from 5-0 to 1-0. This pH-dependent inhibition was accompanied by an increase in pepsin secretion. 4. The pH-dependent inhibition of the Heidenhain pouch response to the liver extract meal was not altered by topical application of a local anaesthetic and atropine or by the intravenous infusion of large doses of atropine, secretin or metiamide, which were shown to cause a marked inhibition of the main stomach response to the liver meal. 5. The results indicate that there is a local and gastrin-independent inhibition mechanism of gastric acid secretion activated by an acidified meal making contact with the oxyntic gland area.