Dietary antioxidants and the biochemical response to oxidant inhalation

We fed female strain A/St mice selenium (Se) test diets containing either no Se (?Se) or 1 ppm Se (+Se) for 11 wk. Both diets contained 55 ppm vitamin E. We then exposed three groups of mice from each dietary regimen to either 0.8 ppm (1568 μg/m³) O₃ (low-level) continuously for 5 d, 10.0 ppm (19,600 μg/m³) O₃ (high-level) for 12 h, or filtered room air, where the latter served as a control for both O₃ exposures. After O₃ exposures we analyzed the lungs for various physical and biochemical parameters, and compared the results to those obtained from the air controls. The results showed that the difference in dietary Se intake produced an eightfold difference in Se content and a three-fold difference in glutathione peroxidase (GP) activity in the lung, but few changes in other lung parameters. With low-level O₃ exposure, NADPH production increased significantly in +Se mice, but did not change in ?Se mice. With high-level O₃ exposure we observed comparable effects for both dietary regimens, including animal mortality, which was 24% for ?Se and 14% for +Se mice. Thus, it seems that diminished GP activity resulting from Se deficiency and the ensuing lack of increase in NADPH production were poorly correlated with mouse tolerance to O₃. The lung Se content increased in both dietary regimens after O₃ exposure, but the increase was greater after high-level O₃ exposure. This suggests a “mobilization” of Se to the lung under O₃ stress. It is possible that such a mobilization contributes to the lung reserve of antioxidants, and hence the comparable mortality in both dietary Se regimens.