Cell Proliferation in the Respiratory Tract of Hamsters Continuously Exposed During 4 Weeks to 0.8 PPM Ozone

Abstract

Male Syrian golden hamsters were exposed to 0.8 ppm ozone, 24 h/day for 4 wk. Cumulative labeling indices were measured during each week of exposure in the lung, the intrapulmonary airways, the trachea, and the nasal passages. In the alveolar zone, ozone did not affect labeling indices beyond the centriacinar region. In the terminal bronchioles and large intrapulmonary airways, labeling indices were significantly higher than in controls throughout exposure to ozone. The largest increase was seen during wk I. In the trachea and the nasal passages, a significant increase in cell labeling was only seen during wk I; thereafter the values returned to control levels. It was concluded that exposure to 0.8 ppm ozone produces signs of proliferative activity during a 4-wk continuous exposure in the epithelium of the intrapulmonary airways, but not in other sites.