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 antioxidant enzyme function was studied in four marine invertebrates, viz. mussel M. edulis (euryoxic herbivore), scallop P. maximus (stenoxic herbivore), crab C. maenas (euryoxic omnivore) and starfish A. rubens (euryoxic carnivore). Se-GPX, Superoxide dismutase and catalase activities were generally highest in the major digestive detoxication tissue of each species (digestive gland, hepatopancreas or pyloric caeca), consistent with pro-oxidant xenobiotics being a major source of oxyradical production. Total GPX activity was more similar between tissues, presumably due to a wider tissue distribution of glutathione S-transferases with GPX activity. Levels of putative Se-GPX mRNA (slot-blot analysis with 1.4 kb human gene probe) paralleled Se-GPX activity in the two mollusc species, indicating regulation of enzyme function at the level of mRNA. In vitro endogenous potential for NAD(P)H-dependent hydroxyl radical production (iron-mediated 2-keto-4-methiolbutyric acid oxidation) was similar in the digestive tissues of the four species, whereas differences in antioxidant enzyme activities were greater, indicating that exogenous sources of oxyradical production may be important in determining levels of antioxidant defences.