Regulation of gastric acid secretion.

The advent of the H2-histamine-receptor antagonists has given new life to the old hypothesis that histamine might be the final common chemical mediator of acid secretion. The available evidence, however, does not prove this hypothesis but does confer on histamine a role in the regulation of acid secretion in normal physiology. Evidence is mounting that, in addition to its stimulatory action, the vagus may play an inhibitory role in acid secretion and gastrin release. Our concepts of the gastric phase of acid secretion have been extended by the discovery of cross distension reflexes in the stomach: the pyloro-oxyntic reflex for acid secretion and the oxyntopyloric reflex for gastrin release. In addition, digested protein has been shown to stimulate directly the oxyntic gland mucosa, but the evidence is against a role for this mechanism in the intact stomach. The hormone(s) responsible for the intestinal phase have not been isolated but the physiological characteristics of entero-oxyntin (a nongastrin, enteric substance that acts on the oxyntic cell) have been defined. Gastric inhibitory polypeptide is an excellent candidate for the entero-gastrone released by fat, but whether it is the sole enterogastrone released is yet to be determined.