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  • Title: Low levels of methylmercury induce DNA damage in rats: protective effects of selenium.
    Author: Grotto D, Barcelos GR, Valentini J, Antunes LM, Angeli JP, Garcia SC, Barbosa F.
    Journal: Arch Toxicol; 2009 Mar; 83(3):249-54. PubMed ID: 18754101.
    Abstract:
    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 mug/day); (Group III) received Se (2 mg/L drinking water); (Group IV) received Se (6 mg/L drinking water); (Group V) received MeHg (100 mug/day) and Se (2 mg/L drinking water); (Group VI) received MeHg (100 mug/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 < 0.05). Groups V and VI did not show a difference in enzyme activity compared with groups III and IV, showing the possible protective action of Se. Comet assay presented a significant difference in DNA migration between group II and group I (P < 0.0001). Groups V and VI showed a significant reduction in MeHg-induced genotoxicity (P < 0.001) when compared with group II. A negative correlation (r = -0.559, P < 0.05) was found between GSH-Px activity and DNA lesion, showing that the greater the DNA damage, the lower the GSH-Px activity. Our findings demonstrated the oxidative and genotoxic properties of MeHg, even at low doses. Moreover, Se co-administration reestablished GSH-Px activity and reduced DNA damage.
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