Antioxidant enzyme activities, metallothioneins and lipid peroxidation as biomarkers in Ruditapes decussatus?

Antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPX)) were studied in the gills and digestive gland of clams Ruditapes decussatus from different sites of the Ria Formosa (south coast of Portugal) in order to validate these enzymes as biomarkers of metal exposure. Two other potential biomarkers, lipid peroxidation expressed as malondialdehyde (MDA), and metallothionein (MT) levels were also measured. This study demonstrates that mitochondrial and cytosolic SOD activity changed while CAT activity (cytosolic and mitochondrial) was higher in the gills of clams from the three sites affected by different sources of contamination. GPXs (total and Se-dependent) were inhibited in the gills of clams from sites A (directly influenced by sewage industrial wastes) and B (directly influenced by harbor facilities). MT and MDA levels were higher in the gills of clams from these two sites and in the digestive gland of clams from the third site (C, main navigation channel and exchange with Atlantic ocean). These results suggest that CAT and GPX activities and MDA levels especially in the gills of clams can be used as biomarkers for monitoring environmental pollution.