Comparison of liver mixed-function oxygenase and antioxidant enzymes in vertebrates

Abstract

We performed a comparative analysis of cytochrome P450, cytochrome b 5, MFO associated enzymes and cytosolic antioxidant enzymes in hepatic microsomes and cytosolic fractions prepared from five animal species representing three vertebrate classes living in tropical conditions (Brazil). The data obtained show that rats have higher hepato-somatic index, specific cytochrome b 5 concentration, and NADPH-dependent cytochrome c (P450) activity compared to ectothermic species, SOD activity similar to those in amphibians, and specific concentration of cytochrome P450 and catalase activity lower than in a toad, but higher than in fishes and a frog. Our data indicate that tropical fishes may have reduced xenobiotic-metabolizing ability compared to the rat and amphibians. In contrast to fish and rat, amphibians have a low ratio (<0.5) of cytochrome b 5 concentration to that of P450. Most species showed cytochrome b 5 sensitivity to oxygen. Thus, the use of sodium dithionate as a reducer, rather than NADPH, may be preferential in b 5 determinations.