Vitamin A is involved in maintenance of epithelial cells on the bronchioles and cells in the alveoli of rats.

We examined the effects of mild vitamin A deficiency and ozone (O3) exposure on the labeling index, a marker of cell proliferation, of epithelial cells on the bronchiole and cells in the alveoli of rat lungs, to assess the role of vitamin A in maintenance of epithelial cells on the distal airway and alveolus. Three-week-old rats were fed a vitamin A-depleted diet for 4 wk to induce mild vitamin A deficiency. After 2 wk rats were exposed to 16.4 mumol O3/m3 for 1 to 14 d. In vitamin A-sufficient rats, labeling indices of epithelial cells on the bronchiole and cells in the alveolus increased significantly in comparison with those of controls exposed to clean air on d 2 and 3 of O3 exposure. In vitamin A-deficient rats as well, labeling indices were increased by O3 exposure, but the magnitude of increase was significantly smaller than for vitamin A-sufficient rats. These results indicate that vitamin A deficiency resulted in decrease of proliferation of epithelial cells on the distal airway and cells in the alveolus of rats when the proliferation of these cells was stimulated by O3 exposure, suggesting an involvement of vitamin A in maintenance of lung epithelial cells.