Lipid peroxidation and metallothionein induction by chromium and cadmium in Oyster Crassostrea virginica (Gmelin) from Mandinga Lagoon, Veracruz

Resumo

Metallothionein and lipid peroxidation are associated to metals toxicity, it is possible that accumulation in tissue might as well be related to their increase. Both biomarkers under Cr and Cd exposure were evaluated in the American oyster Crassostrea virginica (Gmelin) by Semi-static bioassays, 96 h long. Metallothionein content was determined by silver saturation, lipid peroxidation by reactive components to thiobarbituric acid, and metals concentration by atomic absorption spectrophotometry. Metallothioneins increased in digestive gland and abductor muscle under Cr exposure, after 6 h. Under Cd exposure, metallothioneins showed variations, with high values after 48 h in digestive gland, abductor muscle and gill, and important dispersion of data. Lipid peroxidation under Cr exposure reached after 48 h. In Cd, values higher than controls were observed after 6 h exposure. Metallothioneins in gill and digestive gland were positively correlated with the Cr concentration in water and in oysters. In contrast, these proteins correlation turned out to be negative to the Cr Bioconcentration Factor in digestive gland and muscle. The higher peroxidation in oysters which accumulated less, suggests deterioration and a metabolic effort to control the Cr internal concentration. Under Cd exposure, metallothioneins showed positive correlations between water and oysters metal content, and with the Bioconcentration Factor. The correlations, indicates incapability to control the Cd stored levels. The results indicate that the protective role of metallothioneins was limited in the case of this non esencial metal, in oyster originated in native populations from Mandinga Lagoon.