Protection against oxidative stress in liver of four different vertebrates

The possible relation between respiratory capacity and antioxidant;: capaci ty and susceptibility to oxidative stress of the liver has been investigate d in Rattus norvegicus, Gallus gallus domesticus, Lacerta s. sicula, and Ra na esculenta. Accordingly, we measured oxygen consumption and cytochrome ox idase activity, glutathione peroxidase and glutathione reductase activity a nd overall antioxidant capacity, and lipid peroxidation and response to oxi dative stress in vitro in liver. The order of liver oxygen consumption and cytochrome oxidase activity among the different species mras rat > chick > Lizard > frog. The antioxidant defenses supplied by the combined action of glutathione peroxidase and glutathione reductase were not adapted to the re spiratory capacities. In particular, there was no correlation either betwee n the activities of two enzymes or between their activities and oxygen cons umption. In contrast, the overall antioxidant capacity of the liver appeare d to be related to its oxidative capacity, and the malondialdehyde formatio n, an indirect measure of lipid peroxidation, was inversely related to anti oxidant capacity. The response to oxidative stress in vitro indicated that the liver susceptibility to oxidative challenge is higher in ecto thermic t han in endothermic species. Such higher susceptibility appeared to depend o n both lower antioxidant capacity and higher levels of free radical produci ng species. This finding is apparently in contrast with a higher content of cytochromes in endotherms, which are able to determine both respiratory ch aracteristics and sensitivity to pro-oxidants. However, it could indicate t he existence of species-related differences in the tissue content of either preventive antioxidants or hemoproteins able to trap the radicals produced at their active center. J. Exp. Zool. 284:610-626, 1999. (C) 1999 Wiley-Li ss, Inc.