title: Low levels of methylmercury induce DNA damage in rats: protective effects of selenium.
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.
authors.affiliation: Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café s/n, Campus Universitário da USP, 14040-903, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Denise
authors.initials: D
authors.lastname: Grotto
authors.forename: Gustavo R M
authors.initials: GR
authors.lastname: Barcelos
authors.forename: Juliana
authors.initials: J
authors.lastname: Valentini
authors.forename: Lusânia M G
authors.initials: LM
authors.lastname: Antunes
authors.forename: José Pedro F
authors.initials: JP
authors.lastname: Angeli
authors.forename: Solange C
authors.initials: SC
authors.lastname: Garcia
authors.forename: Fernando
authors.initials: F
authors.lastname: Barbosa