Role of the Pyloric Antrum in Regulation of Gastric Secretion

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Abstract
The pyloric antrum which secretes no hydrochloric acid functions as an endocrine organ. Its hormone, gastrin, mediates the gastric phase of gastric secretion. The release of gastrin is stimulated by contact of various food substances with the antral mucosa. Dilute alcohol and liver extract were very effective. The exact nature of this chemical stimulus remains undetermined. Mechanical stimulation of the antrum by distention also produces gastrin. Both types of stimuli apparently are important under physiological conditions. Gastrin formation is inhibited in an acid environment. To achieve inhibition, the antral contents must be at a pH of 1.5 or less. The intact digesting stomach of both man and animals normally reaches a pH in this range and this inhibitory effect of acid probably represents a homeostatic mechanism terminating the gastric phase of gastric secretion. Acid in the antrum will inhibit some other gastric secretory stimuli, suggesting the possibility that the antrum liberates a second hormone which inhibits secretion of acid. Evidence on this point remains controversial and inconclusive and inhibition of the gastrin mechanism by acid is not known to be due to a second antral hormone. Local anesthetics applied to the antral mucosa interfere with the release of gastrin. Although the cell of origin of gastrin is not known, this effect of anesthetics implicates the intramural nerve plexuses as playing a role. Vagus stimulation will release gastrin, further supporting the concept.

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