BACKGROUND AND OBJECTIVE: The frequency of gastrointestinal ulceration is higher in jaundiced patients than in healthy population. The aim of this study was to assess the effect of pretreatment with melatonin, a potent scavenger of reactive oxygen species, on stress-induced gastric ulcers of cholestatic rats. MATERIALS AND METHODS: Cholestasis was induced by surgical ligation of bile-duct and sham-operated rats served as sham animals. The animals received saline or melatonin (1, 3 or 10mg/kg) before stress induction. Three different types of gastroinvasive agents including ethanol, indomethacin or water immersion were used as stress agents to induce gastric ulceration. RESULTS: Gastric mucosal damage induced by different gastroinvasive agents was significantly greater in bile-duct-ligated rats than in sham ones. Melatonin was protective against ethanol-, indomethacin- and water immersion-induced gastric damage in bile-duct-ligated and sham rats, dose-dependently, but the protective effect of melatonin was greater in cholestatic rats than sham rats in all three different series of experiments. CONCLUSIONS: In conclusion, pretreatment of rats with melatonin protected gastric mucosa of cholestatic rats more effectively than the sham ones possibly by a mechanism involving the scavenging of free radicals.
BACKGROUND AND OBJECTIVE: The frequency of gastrointestinal ulceration is higher in jaundicedpatients than in healthy population. The aim of this study was to assess the effect of pretreatment with melatonin, a potent scavenger of reactive oxygen species, on stress-induced gastric ulcers of cholestaticrats. MATERIALS AND METHODS: Cholestasis was induced by surgical ligation of bile-duct and sham-operated rats served as sham animals. The animals received saline or melatonin (1, 3 or 10mg/kg) before stress induction. Three different types of gastroinvasive agents including ethanol, indomethacin or water immersion were used as stress agents to induce gastric ulceration. RESULTS: Gastric mucosal damage induced by different gastroinvasive agents was significantly greater in bile-duct-ligated rats than in sham ones. Melatonin was protective against ethanol-, indomethacin- and water immersion-induced gastric damage in bile-duct-ligated and sham rats, dose-dependently, but the protective effect of melatonin was greater in cholestaticrats than sham rats in all three different series of experiments. CONCLUSIONS: In conclusion, pretreatment of rats with melatonin protected gastric mucosa of cholestaticrats more effectively than the sham ones possibly by a mechanism involving the scavenging of free radicals.