Biochemical effects of combined gases of nitrogen dioxide and ozone. III. Synergistic effects on lipid peroxidation and antioxidative protective systems in the lungs of rats and guinea pigs

Abstract

Rats and guinea pigs were exposed continuously to 0.4 ppm NO2, 0.4 ppm O3 or a combination of the two gases for 2 weeks. The concentration of lipid peroxides in lungs of rats and guinea pigs exposed to NO2 alone or O3 alone did not change. The lipid peroxide level of rats inhaling the combined gases also did not change. However, the level of lipid peroxides in guinea pigs exposed to a combination of the two gases was increased to 2.2 times of the control level, showing a synergistic interaction. No increases of antioxidative protective enzyme activities and of antioxidants (such as NPSH, VE, VC) in guinea pigs exposed to NO2, O3 or the combined gases were found. In rats, no changes in enzyme activities and of the antioxidant contents were observed after NO2 alone, but O3 exposure produced slight increases of NPSH, VC, and GPx-H2O2. On the other hand, in rats exposed to the combined gases, marked synergistic increased of many antioxidative factors such as NPSH, VC, G6PD, GPx-cum.OOH and GPx-H2O2 were found. The results show that those animals which are able to increase antioxidative protective factors in the lung following exposure to the combined gases do not respond with a significant increase in lipid peroxides. On the other hand, in animals with poor induction-ability of these factors lipid peroxides are formed. This might explain why guinea pigs were the most sensitive to the effects of the combined gases. Furthermore, it was shown that in guinea pigs the increased level of lipid peroxides and that in rats the increased activities of antioxidative enzymes and the increased contents of the antioxidants were synergistic following exposure to the combined gases.