Characteristics of bronchoalveolar leukocytes from the lungs of rats inhaling 0.2-0.8 ppm of ozone

The study was aimed at investigating the likely role of the bronchoalveolar leukocytes in the epithelial injury arising from exposure to ozone at low concentrations. Rats were exposed to 0.2–0.8 ppm of ozone for 7 hr/day for up to 4 days. At the selected time points the lungs were lavaged and the bronchoalveolar lavage cell profile was assessed by differential counting. Selected activities of the bronchoalveolar leukocytes, which could contribute to epithelial injury in vivo, were assessed in vitro, including (1) spontaneous and phorbol-stimulated release of superoxide anion, (2) proteolysis of fibronectin, and (3) ability to damage epithelial cells. Exposure to ozone at the highest concentrations caused inflammation in the bronchoalveolar region as shown by an increase in the proportion of neutrophils in the lavage. There was adaptation to the ozone-induced injury as shown by the fact that this inflammation was reduced as the time of exposure increased. No increases in any of the indicators of ability to injure epithelial cells in vivo were seen. There was evidence of decreased ability to mount an oxidative burst in the bronchoalveolar leukocytes from rats inhaling 0.6 ppm of ozone but this was not present in those rats that were inhaling 0.8 ppm. The macrophages from the lungs of rats inhaling the highest concentrations of ozone showed blebbing and this was reflected in an increase in the size compared to controls. We conclude that ozone, at the time points and concentration utilized here, causes inflammation but that the inflammatory cells are unlikely to mediate injury to the epithelial cells.