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

Abstract

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.