ANTIOXIDANT ENZYME-ACTIVITIES IN EMBRYOLOGIC AND EARLY LARVAL STAGES OF TURBOT

The antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), catal ase (EC 1.11.1.6), selenium-dependent glutathione peroxidase (SeGPX; E C 1.11.1.9), glutathione reductase (EC 1.6.4.2) and DT-diaphorase (EC 1.6.99.2), plus total GPS activity (sum of SeGPX and Se-independent GP X activities), were studied in 13 500 g supernatants of embryos and a- day and Ii-day post-hatch larvae of turbot Scophthalmus maximus L., SO D activity decreased progressively during development from embryos to ii-day-old larvae, indicative of a decreased need to detoxify superoxi de anion radical (O-2(-)). In contrast, catalase, SeGPX and glutathion e reductase activities increased progressively from embryos to Ii-day- old larvae, indicative of an increased need to metabolize hydrogen per oxide (H2O2) and organic peroxides. Consistent with the latter changes , levels of lipid peroxides (i.e, thiobarbituric acid reactive substan ces) increased 13-fold from embryos to 3-day-old larvae, whilst total peroxidizable lipid was indicated to decrease. Increases were seen for NADPH-dependent DT-diaphorase (after hatching) and total GPX (between 3 and ii days post-hatch) activities, whilst no change was found in N ADH-dependent DT-diaphorase activity. Overall, the results demonstrate a capacity for early life-stages of S. maximus to detoxify reactive o xygen species (O-2(-) and H2O2) and other pro-oxidant compounds (organ ic peroxides, redox cycling chemicals). Furthermore, qualitative and q uantitative antioxidant changes occur during hatching and development, possibly linked to such events as altered respiration rates (SOD chan ges) and tissue reorganization and development (catalase, SeGPX, lipid peroxidation). (C) 1996 The Fisheries Society of the British Isles