Heavy-metal effects on lipid peroxidation and antioxidant defence enzymes in musselsMytilus galloprovincialis

The use of lipid peroxidation and antioxidant defence enzyme activities in aquatic organisms as molecular biomarkers of environmental pollution has been proved to be of great diagnostic value. Toxicities of Cu(II), Cd(II), Pb(II), and Fe(II) were investigated in mussels Mytilus galloprovincialis with a 24-h short-term bioassays (lethal concentration 50%, LC50) using end-point mortality. Results showed that the LC50 values were: 0.35 mg l−1 for Cu, 1.6 mg l−1 for Cd, 4.5 mg l−1 for Pb, and>6 mg l−1 for Fe. The same metals were used at sub-lethal concentrations to study the modulation of lipid peroxidation and antioxidant enzyme activities in the gills and the mantle of M. galloprovincialis (exposed for a period of 10 d) and compared with a control (unexposed) group. Superoxide dismutase activities increased for Cu and displayed a high variability for Cd, Pb, and Fe, compared with control. Catalase (CAT) activities decreased for Cu, Cd, and Pb, but increased for Fe in both tissues. Lipid peroxidation (measured as MDA levels) increased for all metals in both tissues and were associated with equivalent decreases in antioxidant enzyme activities (especially CAT). These results indicated that mussels stimulated the increase in antioxidant enzyme activities as an adaptive response to metals' oxidative damage. However, these increases were not adequate to prevent oxidation of membrane lipids of soft tissues.