Abstract
1. Melatonin (MT) is a pineal hormone that is also abundant in the gut and has a well known role in scavenging oxygen free radicals. The aim of the present study was to evaluate the potential protective effects of MT against H2O2-induced gastric lesions in rats.
2. An experimental model of gastric ulceration was established in rats using 15% H2O2. Melatonin (12.5, 25 or 50 mg/kg, intagastrically) was administered to rats 30 min before H2O2 challenge.
3. Intragastric administration of H2O2 resulted in haemorrhagic lesions in the fundic area of the stomach. Furthermore, H2O2 induced gastric oxidative stress, as indicated by depletion of reduced glutathione (GSH), inhibition of glutathione peroxidase (GPx) activity and elevation of malonedialdehyde (MDA) levels. These effects were accompanied by decreased gastric tissue levels of prostaglandin (PG) E-2 and nitric oxide (NO), as well as increased levels of tumour necrosis factor (TNF)-alpha. Administration of MT (12.5, 25 or 50 mg/kg) 30 min before H2O2 significantly attenuated the development of gastric lesions in a dose-dependent manner. The protective effects of MT were accompanied by significant inhibition of the H2O2-induced reduction in gastric content of GSH and GPx activity and elevation in MDA levels. Furthermore, MT antagonized H2O2-induced reduction of gastric PGE(2) and NO levels and elevation of TNF-alpha.
4. In conclusion, MT protects rat gastric mucosa against H2O2-induced damage. The observed protective effects of MT can be attributed, at least in part, to its anti-oxidant properties, preservation of PGE(2) and NO levels, as well as inhibition of TNF-alpha induction in gastric tissues.