Low levels of methylmercury induce DNA damage in rats: protective effects of selenium

In this study we examined the possible antigenotoxic effect of selenium (Se) in rats chronically exposed to low levels of methylmercury (MeHg) and the association between glutathione peroxidase (GSH-Px) activity and DNA lesions (via comet assay) in the same exposed animals. Rats were divided into six groups as follows: (Group I) received water; (Group II) received MeHg (100 μg/day); (Group III) received Se (2 mg/L drinking water); (Group IV) received Se (6 mg/L drinking water); (Group V) received MeHg (100 μg/day) and Se (2 mg/L drinking water); (Group VI) received MeHg (100 μg/day) and Se (6 mg/L drinking water). Total treatment time was 100 days. GSH-Px activity was determined spectrophotometrically and DNA damage was determined by comet assay. Mean GSH-Px activity in groups I, II, III, IV, V and VI were, respectively: 40.19 ± 17.21; 23.63 ± 6.04; 42.64 ± 5.70; 38.50 ± 7.15; 34.54 ± 6.18 and 41.39 ± 11.67 nmolNADPH/min/gHb. DNA damage was represented by a mean score from 0 to 300; the results for groups I, II, III, IV, V and VI were, respectively: 6.87 ± 3.27; 124.12 ± 13.74; 10.62 ± 3.81; 13.25 ± 1.76; 86.87 ± 11.95 and 76.25 ± 7.48. There was a significant inhibition of GSH-Px activity in group II compared with group I ( P