Responses of hepatocytes to DDT and methyl mercury exposure.

The aim of the current work was to investigate the effects of dichlorodiphenyltrichloroethane (DDT) and monomethyl mercury (MeHg) on hepatocytes from tropical fish Hypostomus commersoni (cascudo). In order to verify DDT and MeHg impacts on the redox milieu, cells were exposed for 4 days to 50 nM of DDT, 0.25 and 2.5 microM of MeHg and to a combination of 50 nM of DDT and 0.25 microM of MeHg. These concentrations were compared with those previously published (Filipak Neto et al., 2008) for the predator fish Hoplias malabaricus (traíra). The effects were mostly noticeable on reduced glutathione concentration and delta-aminolevulinic acid dehydratase and glutathione S-transferase activity. Catalase activity increased in the group exposed to 2.5 microM of MeHg and hydrogen peroxide levels decreased in all exposed groups. Also, superoxide anion levels decreased in the groups exposed to 2.5 microM of MeHg and DDT *MeHg group. Cell viability decreased only in the DDT exposed group, demonstrating that the antioxidant defense mechanism of H. commersoni hepatocytes is more efficient than H. malabaricus. These results corroborate the resistance of H. commersoni to polluted areas and support the hypothesis that this species is more resistant to DDT and MeHg than H. malabaricus species.