GLUTATHIONE-REDUCTASE, SELENIUM-DEPENDENT GLUTATHIONE-PEROXIDASE, GLUTATHIONE LEVELS, AND LIPID-PEROXIDATION IN FRESH-WATER BIVALVES, UNIO-TUMIDUS, AS BIOMARKERS OF AQUATIC CONTAMINATION IN-FIELD STUDIES

The aim of this study was to evaluate the usefulness of antioxidant pa rameters in the freshwater bivalve, Unio tumidus, as biomarkers of exp osure to pollutants and to study their potential interest in predictin g toxicity. Selenium-dependent glutathione peroxidase (Se-GPx), non-se lenium-dependent glutathione peroxidase (non-Se-GPx), glutathione redu ctase (GRd), catalase, and superoxide dismutase (SOD) activities; redu ced (GSH) and oxidized (GSSG) glutathione levels; and lipid peroxidati on were measured in the gills and digestive glands of Unio. Control mu ssels were encaged and transplanted for 15 and 30 days to sites where the contamination of sediments was analyzed, along a river receiving d omestic and industrial sources of pollution. After 15 days of exposure , all antioxidant parameters of the bivalves transferred to the most p olluted sites had strongly decreased compared with control values. Thi s was particularly true for Se-GPx and GRd activities, which were inhi bited by 60 and 80% in the two tissues, and for GSH levels (80% reduct ion in the gills and 60% in digestive glands). These decreases were as sociated in the gills with lipid peroxidation (measured by malondialde hyde content) and with a high level of contamination of sediments by p olycyclic aromatic hydrocarbons and polychlorinated biphenyls. In the mussels exposed at the least polluted sites, the same parameters decre ased in the gills, but to a lesser extent: 50% for Se-GPx and 32% for GRd activities, and 45% for GSH levels. The gills appeared more sensit ive than the digestive glands. After 30 days of exposure, while Se-GPx , GRd, and GSH remained reduced, a significant induction of non-Se-GPx and catalase activities was recorded in the gills, which reflected an adaptation of the transplanted species to their unsafe environment, A ll the results indicated that antioxidant defense components, namely, Se-GPx, GRd, and GSH, are sensitive parameters that could be useful bi omarkers for the evaluation of contaminated aquatic ecosystems. The re lationship between the degree of deficiency of anti-oxidant defenses a nd lipid peroxidation suggests that these parameters could also be bio markers for toxicity. (C) 1997 Academic Press.