Antioxidant responses of the Mediterranean mussel, Mytilus galloprovincialis, to environmental variability of dissolved oxygen

Physiological responses of Mytilus galloprovincialis against environmental dissolved oxygen partial pressure (pO2) variation were studied in terms of the modulated induction of the main antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (GPX). Field in vivo studies were performed at two sites of the Lagoon of Venice, characterized by different aquatic environmental conditions implying different pO2. SOD and GPX are more active in gills, and their complementary role is discussed. CAT is more active in the digestive gland, where the enzyme dismutates H2O2 derived from divalent reduction of O2 performed by various oxidases in peroxisomes. Antioxidant enzyme activities are correlated with water dissolved oxygen (DO), especially in the gills. This tissue, because of its anatomical localization and its physiological role, responds to DO variations modulating the induction of the antioxidant enzymes as a protection mechanism against potential toxicity due to increases in ROS formation.