Biochemical effects of combined gases of nitrogen dioxide and ozone. II. Species differences in lipid peroxides and antioxidative protective enzymes in the lungs.

Changes in lipid peroxide (thiobarbituric acid reactant) levels, in the content of non-protein sulfhydryls (NPSH) and total proteins, and in the activities of antioxidative protective enzymes were examined in the lungs of four animal species exposed to a mixture of NO2 and O3 for 2 weeks. Male mice, hamsters, rats and guinea pigs were used. Thiobarbituric acid (TBA) reactant levels were increased significantly in the lungs of mice and guinea pigs, but not in hamsters and rats. NPSH contents were increased markedly in hamsters, mice and rats, but not in guinea pigs. The activities of antioxidative protective enzymes also changed with the exposure. The most characteristic change was the significant increase in glutathione peroxidase (GPx-H2O2) activity in hamsters and rats - species which did not exhibit increases in their TBA reactant levels. The increase in this enzyme activity in mice was significant, but not very large. Furthermore, guinea pigs were genetically deficient in this enzyme, and the increase in glycolytic enzymes for regenerating NADPH was also lowest in guinea pigs. The glutathione S-transferase (GSH-Tase) activity in mice and guinea pigs was decreased by exposure to the combined gases. These results suggest that the increases in lipid peroxide levels in mice and guinea pigs may be due to a lesser ability to regenerate protective reducing substances, such as NPSH and NADPH, than that of hamsters and rats. Induction of protective enzyme activities on exposure to the combined gases was also poor in mice and guinea pigs.