Surface-tension measurements of pulmonary lavage from ozone-exposed rats

Ozone, an important component of photochemical air pollution, has been shown to cause morphological and functional changes in the lung after acute, high-level exposure in controlled animal studies. Previous exposures of rats to 0.8 ppm ozone for 18 h showed trends toward decreased lung volumes, as well as modifications in phospholipid composition of lung lavage fluid. These results suggested that exposure to ozone may have diminished the ability of surfactant to reduce surface tension. The purpose of this pilot study was to determine if changes in the surface tension of lavaged pulmonary surfactant occur with ozone exposure. The lavage fluid from rats exposed to ozone at 0.8 ppm for 18 h had a 360% increase in protein and a 30% increase in lipid phosphorus content. Lung lavage samples from ozone-exposed rats were more potent in reducing surface tension as measured on a Wilhelmy plate balance. This difference was evident whether determined with half the total lavage or with equivalent microgram amounts of lipid phosphorus. It is concluded that at this dose and duration of ozone exposure, contrary to our hypothesis, surface-tension-lowering ability of surfactant increases and therefore does not appear to be a contributory factor in the previously observed changes in pulmonary function.