Misoprostol prevents damage to the gastric mucosa by stabilizing the mast cells.

Prostaglandins have been shown to prevent the damage to the gastric and intestinal mucosa which has been induced by diverse necrotizing substances. These damaging stimuli increase the liberation of histamine from mast cells. Because of its well known effects on cellular permeability, histamine may serve the initial stimulus for mediating cellular damage. The aim of our study was to investigate the effect of misoprostol, a synthetic PGE1 analog, on tissue histamine concentration and mast cell counts after damage to the gastric mucosa induced by stress, histamine, aspirin and concentrated ethanol in guinea pigs. Misoprostol or its matching placebo were administered intragastrically 3 minutes prior to the ulcerogenic stimulus. After the induction of the injury, the animals were sacrificed, stomachs were examined for ulceration. Gastric and duodenal histamine concentrations were determined. Mast cells from these organs were stained and counted. All four ulcerogenic stimuli resulted in significant gastric ulcer formation. This ulcerogenic action was accompanied by a significant decrease in mucosal histamine concentration and mast cell counts. Misoprostol induced a dose-dependent inhibition of gastric damage, histamine depletion and mast cell destruction. These results indicate that the stabilization of mast cells by misoprostol is an important mechanism for its mucosal protective effects against ulcerogens.