Antiulcer Effects of Melatonin in Wistar Rats –The Roles of Gastric Mucous, Antioxidants and Zinc

Melatonin is known as a potent scavenger of reactive oxygen species. Zinc has also been reported to be involved in tissue regeneration. This activity has been suggested partly as its gastroprotective mechanism. The digestive system has been estimated to produce about 400 times of this neurohormone than the pineal gland. In this study, we report the role of gastric anti-oxidant enzymes, luminal mucosa zinc level and gastric mucus cell counts in the anti- ulcer effects of melatonin in rats. The experimental Wistar rats were divided into five (5) study groups. Each group was further divided into 5 subgroups (n=5) viz: /l Control, Melatonin (20 and 40mg/kg) pre-treated, Ranitidine pre-treated and Omeprazole pre-treated. Drugs were administered orally for 21 days. The effect of melatonin was investigated on indomethacin-induced gastric ulcer and gastric mucus cell counts in rats were measured. The luminal mucosa zinc levels, gastric antioxidant enzymes (SOD and Catalase), and oxidative biomarker for lipid peroxidation; Malondialdehyde (MDA) were determined. Our results showed suppression of oxidative stress (ROS) or its inhibition after 21 days of melatonin pre-treatment in rats. Catalase exhibited significantly stronger activity better than superoxide dismutase. Our study also shows enhanced gastric mucus cell counts in the pre-treated rats. The anti-ulcer mechanisms of melatonin may be due to stimulation of gastric mucus production via raised mucus cell counts, in addition to melatonin reactive oxygen species scavenging ability. It is however, not associated with changes in luminal mucosa zinc level.