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 NO 2, 0.4 ppm O 3 or a combination of the two gases for 2 weeks. The concentrations of lipid peroxides in lungs of rats and guinea pigs exposed to NO 2 alone or O 3 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 NO 2, O 3 or the combined gases were found. In rats, no changes in enzyme activities and of the antioxidant contents were observed after NO 2 alone, but O 3 exposure produced slight increases of NPSH, VC, and GPx-H 2O 2. On the other hand, in rats exposed to the combined gases, marked synergistic increases of many antioxidative factors such as NPSH, VC, G6PD, GPx-cum · OOH and GPx-H 2O 2 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 sentitive to the effects of the combined