Electron Microscopic Studies on the Effects of Ozone on the Lungs of Rsts Fed a Vitamin E-Deficient Diet
1976 Volume 14 Issue 7 Pages 355-365
Details
1976 Volume 14 Issue 7 Pages 355-365
Lipid peroxidation as an effect caused by the exposure of respiratory tissue to ozone has been suggested by several investigators. Vitamin E is believed to function as a “scavenger” of free radicals, thereby interfering with the propagation of the peroxidation reaction. The protective effect of vitamin E on ozone toxicity in rats was investigated at the ultrastructural level by scanning and transmission electron microscopy. Adult rats (130g) were placed randomly into two dietary groups. One group was fed a diet free of vitamin E, and the other, a diet containing 100mg of dl-α-tocopherol (vitamin E) acetate per kilogram of diet. After 98 days of dietary treatment, both groups were exposed to 0.29±0.08 ppm (mean±SD) ozone for 3 hours daily in an acrylic exposure chamber for 16 consecutive days. Animals from each group were killed immediately after ozone exposure, on the 5th, 11th and 16th days.
The lungs were removed, fixed at a distending pressure until the pleural surface became smooth and processed for electron microscopy. The following ultrastructural findings were more prominent in the vitamin E-depleted group than in the group whose diet contained the vitamin:
1. Numerous small round bodies were found scattered on the bronchial surface and cytoplasmic protrusions of non-ciliated bronchial epithelium were increased in number, suggesting increased bronchial secretions. Clara cells were accompanied with many small swellings and small round bodies on their surface.
2. Swelling or denudation of the cytoplasm of the Type I alveolar surface lining cells with exposure of the basement membrane (so-called alveolar ulcer), and focal swelling of the cytoplasm of the Type II alveolar cells. The extent of these changes was most marked after 5 days of exposure.
3. Considerable cell debris was found in the alveolar spaces, due possible to cellular damage.
4. After 16 days of exposure, both alveolar interstitium and basement membrane were edematous and were greatly thickened.
The morphological results tend to support the biochemical evidence that one effect of vitamin E is to prevent or alleviate the cytotoxic effects of ozone.
