Antioxidant defences in marine fish-I. Teleosts

1. A variety of tissues from six marine teleost fishes of diverse ecophysiological characteristics was assayed for Superoxide dismutase, catalase, and glutathione peroxidase activities. 2. Blood (3-37 nmol g^-1 Hb), liver, heart, red muscles, ovaries and capillaries from the choroid and gas-bladder retia displayed higher superoxide dismutase (2-8 nmol g^-1 wet tissue) contents as compared with other tissues. 3. Catalase was present at high levels in blood (c. 300-1000 pmol g^-1 Hb) and liver (c. 100 to 250 pmol g^-1 wet tissue), at moderate levels in heart, spleen, kidney and in choroid and gas-bladder retia (30-40 pmol g^-1 wet tissue), and at low levels in the other tissues. Glutathione peroxidase content was relatively low (1-30 pmol g^-1 wet tissue) in the tissues and structures examined excepting blood. 4. The content of antioxidant enzymes of blood, liver, heart and red muscle seem to be correlated to the fish swimming and metabolic activities.