Effects of melatonin consumption on some oxidative stress biomarkers of stress-exposed pregnant rats.

Melatonin acts as a free radical scavenger and nuclear and mitochondrial DNA from free radicals-induced damage. This study was designed to test the hypothesis that melatonin may mitigate the effect of restraint stress in pregnant rats by mechanisms associated with stimulation of antioxidant enzymes and reduction in malondialdehyde (MDA) levels. Pregnant Wistar rats aged between 10-12 weeks and weighing 125±5.5g (mean ±SEM), were randomly divided into three groups (n= 8 each) that had the following treatments: non- stress with vehicle (NSV), stress with vehicle (SV) and stress with melatonin (SM). During the second week of pregnancy, the rats were individually restrained for 1 hour a day for one week. Melatonin (10mg/kg) was administered orally to the treatment group (SM) every day throughout the stress exposure period while the control groups (NSV and SV) received the vehicle (water). Three weeks after delivery, the rats were euthanized and the antioxidant enzymes [catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)] and MDA levels were measured. The CAT values SV rats were significantly (P<0.001) lower than in NSV and SM rats. The values for GPx and SOD followed the same pattern with CAT. The MDA value obtained from the SV rats were significantly (P<0.0001) higher than the values obtained from NSV and SM rats. The MDA values obtained from the SM rats were significantly (P<0.05) higher than in NSV rats. Results suggest that melatonin helps in countering the effects of restraint stress in pregnant Wistar rats by increasing the serum levels of CAT, GPx and SOD while reducing the serum level of MDA. It is concluded that stress- induced reduction in antioxidant enzymes and attendant increase in lipid peroxidation are mitigated by melatonin.