EFFECTS OF THE CA2+ CHELATORS EGTA AND EDTA ON ETHANOL-INDUCED OR STRESS-INDUCED GASTRIC-MUCOSAL LESIONS AND GASTRIC-SECRETION

Ca2+ modulates gastric function and dysfunction as well as the release of cysteine proteases and metalloproteinases which have been implicated in the pathogenesis of gastric mucosal lesions. We thus tested the hypothesis that pretreatment with the Ca2+ chelators, ethylene diamine tetraacetic acid (EDTA) and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) might reduce the experimental gastric mucosal damage induced by restraint cold stress or 1.0 ml of 75% ethanol. Other rats were prepared with chronic indwelling gastric cannulas and the effects of EDTA and EGTA on conscious basal gastric acid output were assessed. In addition, rats were pretreated with EGTA or EDTA prior to pylorus ligation and their effects on acid and pepsin output assessed. Both EDTA and EGTA reduced significantly the extent of ethanol-induced gastric mucosal damage as well as the degree of stress-induced gastric lesions. To further characterize the mechanism of Ca2+ chelator protection against ethanol-induced gastric lesions, some rats were vagotomized or adrenalectomized prior to treatment with EGTA or EDTA, followed by ethanol or stress. Both adrenalectomy and vagotomy abolished gastroprotection by EGTA and slightly reduced that induced by EDTA in both models of experimental gastric mucosal injury. Both EDTA and EGTA reduced significantly basal gastric acid output, an effect which persisted for at least 2 h following their administration. Both compounds also decreased significantly acid and pepsin output in pylorus-ligated rats. We conclude that Ca2+ chelators attenuate both acid-dependent and acid-independent gastric lesions. The effects of EGTA and EDTA likely involve, at least in part, vagal and glucocorticoid/catecholamine mediation, since vagotomy and adrenalectomy completely blocked and reduced, respectively, their protective influence on the gut.