Increased Elastase Inhibitory Capacity of Lung Lavage Fluid Following Acute Ozone Exposure: Role of Serum Transudation

Abstract The elastase inhibitory capacity of lung lavage fluid has been reported to increase significantly following acute exposure to ozone (O3) (Nadziejko et al., 1992). In the present study, we determined whether this increase was due to transudation of serum proteins into the lung by measuring the protein content and elastase inhibitory capacity (EIC) of lavage fluid and serum following acute exposure of rats to 0.6 ppm O3. These data indicated that the magnitude of the observed increase in lavage fluid EIC was very similar to the increase in EIC that would be expected to occur if serum transudation were the only cause of increased protein content in the lavage fluid of O3-exposed rats. Polyacrylamide gel electrophoresis (PAGE) of lavage fluid and serum showed that almost all of the lavage fluid proteins that were increased in amount 18 h after O3 exposure were the same molecular weight as serum proteins and had the same relative intensities as protein bands from serum. The possibility that the increased EIC of lavage fluid that followed acute O3 exposure was due to enhanced production of antiproteases by pulmonary macrophages was also examined. Pulmonary macrophages from O3- and air-exposed rats were cultured at a density of 1 × 106 cells/ml for 4 h. The EIC of macrophage-conditioned medium was below the level of detection in all samples. The PAGE of macrophage-conditioned medium showed two faint bands with molecular weights of 15,000 and 200,000. No bands with molecular weights similar to α1 AT were seen in any samples of macrophage-conditioned medium. Thus, it is unlikely that macrophages produce sufficient α1 AT to account for the increased lavage fluid EIC following O3 exposure. The results of this study indicate that serum transudation is the main factor responsible for the increased EIC of lavage fluid from O3-exposed rats.