The effects of intermittent nitrogen dioxide exposure on vitamin E-deficient and -sufficient rats

In two separate experiments rats fed vitamin E-deficient, normal or high vitamin E-supplemented diets were intermittently exposed to 15 ppm ± 1.0 ppm nitrogen dioxide (NO₂) over a 5-week (4 days/week, total of 31.5 h exposure) or an 18-week (5 days/week, total of 93.5 h exposure) period. In the 5-week, NO₂-exposed rats, the blood methemoglobin levels were not influenced by NO₂ exposure or the level of vitamin E in the diet. Tissues of the rats exposed to NO₂ for 18 weeks showed some histological changes; in the lung, increased atelectasis and alveolar thickening and in the liver, increased granular changes, karyolysis and karyorhexis. These differences were suppressed by increasing levels of dietary vitamin E. Tissue lipofuscin pigment (LFP) concentrations were not affected by NO₂ exposure or dietary vitamin E. Fatty acid distribution of lung lipid extracts showed no changes due to NO₂ exposure; however, some effects of dietary vitamin E could be seen. The results suggest that intermittent NO₂ exposure, under the described conditions, did not cause ultimate changes of the biochemical parameters measured.