Antioxidant defences role during post anoxic recovery in bivalve mollusc Scapharca inaequivalvis

Euryoxic organisms are able to withstand hypoxic conditions until the restoration of normal O₂ levels, when the re-introduction of oxygen causes a decisive burst in reactive oxygen species (ROS). The consequent oxidative damage is countered by defence systems constituted by antioxidant enzymes, such as SOD, CAT, Se-GPx and G6PDH. Specimens of Scapharca inaequivalvis were exposed to anoxia for 3, 6 and 24 hours and subsequent reoxygenation for 1, 3, 5 and 24 hours. It has been investigated SOD, CAT, Se-GPx and G6PDH activity and MnSOD and CuZnSOD expression in the digestive gland. The results showed SODs activity to be high during both anoxia and reoxygenation. CAT and Se-GPx increase significantly overall during recovery. Only CuZnSOD expression was greater after 6 and 24 hours of anoxia. The presence of high levels of antioxidant enzymes during anozia suggests that the response of S. inaequivalvis is typical of euryoxic animals and represents an interesting model for studying the processes of ischaemia/reperfusion in mammals.