Gastric mucosal damage by ethanol is mediated by substance P and prevented by ketotifen, a mast cell stabilizer.

To elucidate the possible role of substance P in the pathogenesis of acute gastric mucosal damage, rats were treated intragastrically with 1.0 mL 96% ethanol, 0.6N HCl, or 25% NaCl, with or without IP coadministration of substance P, senktide, or septide (1 mumol/L per 100 g). All three peptides were found to double the mean lesion area when compared with that induced by ethanol, whereas substance P antagonist (1 mumol/L per 100 g) prevented the expansion of damage extent. The increased damage was associated with increased gastric mucosal levels of platelet activating factor, leukotriene B4, and leukotriene C4. Substance P antagonists also reduced by half the extent of the gastric damage induced by ethanol when administered by itself. WEB 2086 (platelet-activating factor antagonist; Boehringer Ingelheim KG, Germany), hydroxyzine (H1 blocker), and cimetidine (H2 blocker) reduced lesion area by 50%, but only in rats treated with both substance P and ethanol. Ketotifen (mast-cell stabilizer) (100 micrograms/100 g), administered orally 30 minutes before damage induction, totally abolished the extent of the damage induced by either ethanol or the coadministration of ethanol and peptides in the surface epithelium of the entire mucosa. The protective effect of ketotifen was accompanied by significant reduction in mucosal generation of platelet-activating factor, leukotriene C4, and leukotriene B4. Similar mucosal protection was afforded by ketotifen against damage induced by 0.6N HCl, 25% NaCl, or indomethacin. Therefore, it is suggested that substance P is involved in the pathogenesis of acute ethanol-induced gastric mucosal damage. The effective mucosal protection provided by ketotifen indicates the important role of mast cells and their mediators in the pathogenesis of acute gastric mucosal damage and may have therapeutic implications.