PROOXIDANT AND ANTIOXIDANT PROCESSES IN GAS GLAND AND OTHER TISSUES OF COD (GADUS-MORHUA)

Partial reduction of molecular oxygen produces reactive oxyradicals, i ncluding the superoxide anion radical (O2-) and hydroxyl radical (.OH) . The gas gland functions under hyperoxic and acidic conditions and th erefore is likely to be subjected to enhanced oxidative stress. Aspect s of pro- and antioxidant processes in gas gland were compared with ot her tissues likely to be subject to differing degrees of oxyradical pr oduction, viz. liver (site of chemically-mediated oxyradical productio n), gills and skeletal muscle. Antioxidant enzyme activities (superoxi de dismutase, catalase, selenium-dependent and total glutathione perox idase) per g wet weight were highest in liver and lowest in muscle. Ca talase and glutathione peroxidase activities per g wet weight were hig her in gills than in gas gland, whereas the reverse was seen for super oxide dismutase. Cytosolic superoxide dismutase activities per mg prot ein were two- and nine-fold higher in gas gland than in liver and gill s. The pH characteristics of the antioxidant enzymes were generally si milar in all the tissues. Glutathione, vitamin E and unsaturated (pero xidizable) lipid levels were generally highest in liver followed by ga s gland. Lipid peroxidation (malonaldehyde equivalents) was evident in all tissues except gas gland. Hydrogen peroxide and O2- were involved in the NAD(P)H-dependent ferric/EDTA-mediated formation of .OH (as me asured by 2-keto-4-methiolbutyrate oxidation) by mitochondrial and pos tmitochondrial fractions of gas gland. Tissue maximal potentials for . OH production paralleled superoxide dismutase but not catalase or glut athione peroxidase activities. Overall, the results confirm the presen ce of effective antioxidant defenses in gas gland and support previous workers' contentions of a central role for superoxide dismutase in th is process.