Effects of ozone on cell renewal in pulmonary alveoli of aging mice.

Groups of aging male mice were exposed to different concentrations of ozone (O3) for six hours. Following exposure, the animals were killed at intervals of 1, 24, 48, and 72 hours. Prior to killing, cells synthesizing DNA were labeled with tritiated thymidine. Immediately after exposure, the number of cells that could be labeled with tritiated thymidine was significantly fewer than in the controls. Inhibition of cell labeling was approximately the same at each concentration of O3 tested. By 72 hours, most of the labeling indexes had increased, approaching or surpassing control levels. These results suggest that one of the initial responses of alveolar tissue to O3 is a reduction in DNA synthesis.