SUPPRESSIVE EFFECT OF MELATONIN ADMINISTRATION ON ETHANOL-INDUCED GASTRODUODENAL INJURY IN RATS IN VIVO

1 Melatonin protection against ethanol-induced gastroduodenal injury was investigated in duodenum-ligated rats. 2 Melatonin, injected i.p. 30 min before administration of I mi of absolute ethanol. given by gavage, significantly decreased ethanol-induced macroscopic, histological and biochemical changes in the gastroduodenal mucosa. 3 Ethanol-induced lesions were detectable as haemorrhagic streaks, Ethanol administration damaged 36% and 25% of the total gastric and duodenal surface, respectively. Melatonin treatment reduced ethanol-induced gastric and duodenal damage to 14% and 8%. respectively When indomethacin was given together with ethanol, the gastric damaged area was 44% of the total surface, while the duodenal damaged area was 35%; melatonin administration reduced the damage to only 13% of the total gastric surface and to 12% of total duodenal surface. 4 Both stomach and duodenum of ethanol-treated animals showed polymorphonuclear leukocyte (PMN) infiltration. The number of PMN increased more than 600 and 200 times in stomach and duodenum, respectively, following ethanol administration. Melatonin treatment reduced ethanol-induced PMN infiltration by 38% in the stomach and 20% in the duodenum. In indomethacin-ethanol-treated rats, the number of PMN increased by 875% compared to control group in the stomach and by 264% in duodenum. Melatonin administration reduced the indomethacin-ethanol-induced PMN rise by 57% in the stomach and 40% in the duodenum. 5 Gastroduodenal total glutathione (tGSH) concentration and glutathione reductase (GSSG-Rd) activity were significantly reduced following ethanol and indomethacin-ethanol administration. Melatonin ameliorated both the decrease in tGSH concentration as well as the reduction of GSSG-Rd activity elicited by ethanol both in the stomach and duodenum: melatonin was effective ire against indomethacin-ethanol-induced damage only in the stomach. 6 Ethanol-induced gastroduodenal damage is believed to be mediated by the generation of free radicals. Recently. 3 number of in vivo and in vitro experiments have shown melatonin to be an effective antioxidant and free radical scavenger; thus, we conclude that the protection by melatonin against ethanol-induced gastroduodenal injury is due, at least in part, to its radical scavenging activity.