Role of endogenous prostaglandins in gastric secretion and mucosal defense.

Prostaglandins are found in high concentration in the gastric mucosa and gastric juice. Exogenous prostaglandins inhibit acid secretion, stimulate mucus and bicarbonate secretion, alter mucosal blood flow, and provide dramatic protection against a wide variety of agents which cause acute mucosal damage. The physiological role of prostaglandins is still being elucidated. There is now strong evidence that endogenous prostaglandins modulate acid secretion by blocking the histamine-stimulated increase in cyclic AMP within the parietal cell. This function is probably controlled by intraluminal pH. It is likely that mucus and bicarbonate secretion by both stomach and duodenum are influenced by endogenous prostaglandins. A physiological role of prostaglandins in mucosal protection is less certain. Prostaglandins are released by trivial injury, and this probably serves a defensive function. A mucosa which is prostaglandin-depleted is more susceptible to damage, but does not spontaneously ulcerate. It is conceivable that peptic ulcer disease may be in part caused by an impaired mucosal prostaglandin response to food.