The role of mast cells in mucosal permeability changes during ischemia-reperfusion injury of the small intestine.

The objective of this study was to investigate the significance of mast cell-induced reactions in the mucosal functional and morphological alterations induced by 30 min segmental ischemia and 120 min reperfusion in anesthetized dogs. The rates of changes in permeability of the mucosa to sodium fluorescein (NaFL) in the plasma-to-lumen and lumen-to-plasma directions were studied, the local hemodynamics, intramucosal pH (pHi) alterations, mast cell number and degranulation, and degree of tissue injury were determined. The effects of pretreatments with cromolyn (a peritoneal-type mast cell stabilizer), quercetin (a mucosal-type mast cell stabilizer), and dexamethasone (an aspecific membrane stabilizer and mast cell depleter) were evaluated. We found that ischemia-reperfusion induced significant tissue injury, elevated the segmental vascular resistance, and decreased pHi. The plasma-to-lumen clearance of NaFL increased significantly during ischemia and reperfusion. Cromolyn and quercetin pretreatments significantly inhibited the permeability changes, but did not influence the pHi and morphological alterations induced by ischemia-reperfusion. Dexamethasone pretreatment did not influence the number of mast cells, but the degree of mast cell degranulation and fluorescein leakage decreased. We conclude that intestinal mast cells and mast cell-induced reactions contribute to the mucosal permeability alterations during reperfusion, but play only a minor role in ischemia-reperfusion-induced structural injury.