DEFENSES AGAINST OXIDATIVE STRESS IN THE ANTARCTIC SCALLOP ADAMUSSIUM-COLBECKI AND EFFECTS OF ACUTE EXPOSURE TO METALS

Since a general pathway of toxicity induced by pollutants is the enhan cement of reactive oxygen species, biochemical responses associated wi th variations in the antioxidant cellular system have been often propo sed as biomarkers of pollutant-mediated toxicity associated with oxida tive stress. Antarctic organisms live in an extreme environment charac terized by low water temperature, high level of dissolved oxygen, pres ence of ice and strong seasonal changes in light intensity and availab ility of food, conditions which could influence both the formation of reactive oxygen species and the mechanisms for their removal. In this respect and considering the utility of this as a key species for monit oring marine Antarctic environment it was of interest to investigate t he antioxidant defense system of the scallop Adamussium colbecki. The parameters examined in the digestive gland of the scallop were the con centration of glutathione and the activity of several glutathione depe ndent and antioxidant enzymes (glyoxalase I and II, glutathione S-tran sferases, glutathione peroxidases, glutathione reductase, catalase, su peroxide dismutase). Very high levels of catalase suggest a possible a daptation to Antarctic extreme conditions, while the high activities o f glutathione S-transferases are more probably related to the feeding behavior of Pectinids. Enzymes from Adamussium colbecki generally appe ared to be active at low temperatures but, with a few exceptions, thei r activities increased with rising temperature. Exposure of A. colbeck i to sublethal concentrations of Cu or Hg resulted in a significant re duction in the levels of total glutathione and in the activity of cata lase and glutathione S-transferases. Antioxidant responses of A. colbe cki could represent a useful tool in assessing the biological impact o f environmental pollutants in the Antarctic ecosystems.