Effects of repeated ozone exposure on pulmonary function and bronchial responsiveness in mice sensitized with ovalbumin.

We examined the effect of repeated ozone exposure on the respiratory system in mice, sensitized with ovalbumin (OA). OA-sensitized mice and saline-treated control mice were exposed to 1.0 ppm ozone or clean air for 6 h daily and five days weekly for five weeks. Subsequently, these mice were exposed to 1.0 ppm ozone for 1 h, and pulmonary function was evaluated by pneumotachography during ozone exposure and arterial blood gas analysis and histopathological examination were performed. OA sensitization or repeated ozone exposure did not affect baseline pulmonary function. In OA-sensitized mice receiving repeated ozone exposure, acute ozone exposure increased respiratory resistance and decreased dynamic compliance, with significant differences in both parameters compared with, after repeated ozone exposure without OA sensitization. In mice without repeated exposure, there was no difference in the effect of acute ozone exposure according to the use of OA sensitization. After 1-h exposure, arterial blood gas analysis showed a significant decrease in PaO2 in mice undergoing OA sensitization alone, with no significant reduction of this parameter in mice receiving repeated exposure. Histopathologically, alveolar epithelial hyperplasia occurred in repeatedly exposed mice. These results indicated that respiratory allergy might be a risk factor, which aggravates the effects of repeated ozone exposure.