GLUTATHIONE-PEROXIDASE AND OTHER ANTIOXIDANT ENZYME FUNCTION IN MARINE-INVERTEBRATES (MYTILUS-EDULIS, PECTEN-MAXIMUS, CARCINUS-MAENAS AND ASTERIAS-RUBENS)

Selenium-dependent glutathione peroxidase (Se-GPX) and other antioxida nt enzyme function was studied in four marine invertebrates, viz. muss el M. edulis (euryoxic herbivore), scallop P. maximus (stenoxic herbiv ore), crab C. maenas (euryoxic omnivore) and starfish A. rubens (euryo xic carnivore). Se-GPX, superoxide dismutase and catalase activities w ere generally highest in the major digestive detoxication tissue of ea ch species (digestive gland, hepatopancreas or pyloric caeca), consist ent with pro-oxidant xenobiotics being a major source of oxyradical pr oduction. Total GPX activity was more similar between tissues, presuma bly due to a wider tissue distribution of glutathione S-transferases w ith GPX activity. Levels of putative Se-GPX mRNA (slot-blot analysis w ith 1.4 kb human gene probe) paralleled Se-GPX activity in the two mol lusc species, indicating regulation of enzyme function at the level of mRNA. In vitro endogenous potential for NAD(P)H-dependent hydroxyl ra dical production (iron-mediated 2-keto-4-methiolbutyric acid oxidation ) was similar in the digestive tissues of the four species, whereas di fferences in antioxidant enzyme activities were greater, indicating th at exogenous sources of oxyradical production may be important in dete rmining levels of antioxidant defences.