Antioxidant levels from different Antarctic fish caught around South Georgia Island and Shag Rocks

Antarctic fish have been isolated for over several million years in an envi ronment with a very low and constant temperature and high oxygen concentrat ion. In such conditions the oxidative stress might be an important factor a ffecting their metabolic adaptive strategies. Activity of the antioxidant e nzymes super-oxide dismutase (SOD), catalase (CAT) and glutathione peroxida se (GPx), vitamin E levels and total antioxidant capacity (TRAP) were measu red in liver, gill, heart and muscle homogenates of red-blooded (Notothenii dae) and white-blooded (Channichthyidae) Antarctic fish. SOD activity was a lso measured in blood samples. Gill SOD activity was threefold higher in ch annichthyids than in nototheniids while CAT and GPx were significantly high er in the gills of channichthyids. The increased SOD activity of channichth yids probably reflects the large PO2 gradient across their gills. The H2O2 produced seems to be preferentially eliminated by diffusion, according to t he low levels of CAT and GPx found in the gills of these species. In contra st, blood SOD was about fivefold higher in the latter group, which possesse s erythrocytes and thus a much higher oxygen-carrying: capacity. CAT activi ty was always higher in nototheniids except in muscle. However, vitamin E d id not show clear differences between families except for the pattern obser ved in muscle. The higher content of vitamin E in this tissue shown in chan nichthyids is related to the higher volume density of mitochondria reported for this group, since vitamin E is responsible for preventing membrane lip id peroxidation. Accordingly, TRAP (representative of hydrosoluble antioxid ant capacity) was also higher in muscle of channichthyids. This is probably related to the (a hydrosoluble compound) vitamin E. acid role of ascorbic in regenerating vitamin E.