LUNG SURFACTANT COMPONENTS IN BRONCHOALVEOLAR LAVAGE LAVAGE AFTER INHALATION OF NO2 AS MARKERS OF ALTERED SURFACTANT METABOLISM

To study the effects of nitrogen dioxide (NO2) inhalation on lung lava ge surfactant components as markers of an altered surfactant metabolis m in type II pneumocytes, rats were exposed to atmospheres with increa sing NO2 concentrations (0.8, 5.0, and 10.0 ppm) over 1 and 3 days. Af ter exposure lung lavage was performed and surfactant components as we ll as lavagable cells analyzed. An increased number of total lavage ce lls was found with increasing concentration and duration of NO2 exposu re. Cell distribution showed an elevation in the number of granulocyte s and lymphocytes whereas the number of macrophages was diminished. Th e amount of total lavage protein revealed an increase related to NO2 c oncentration and duration. Also the content of lavage phospholipid was increased, with a decreased portion of phosphatidylcholine (PC). Furt her analyses of PC showed a diminished composition of saturated fatty acids but an elevated content of the unsaturated portion. Functional s tudies on surfactant phospholipid extracts exhibited comparable values for the surface tension at equilibrium, as well as for the maximal an d minimal surface tension of animals exposed to 0.8 ppm NO2 and contro ls. Higher NO2 concentrations (5 and 10 ppm) resulted in increased val ues:for surface tension compared to controls. This was also observed w ith purified surfactant that was obtained from controls and from NO2-e xposed rats. These experiments show that in vitro exposure of purified surfactant to NO2 atmospheres was more effective than exposure in viv o. When the structure of the surfactant proteins A was studied it was found not to be altered by the NO2. The data clearly demonstrate that NO2 inhalation impaired function of surfactant components that may be used as markers of altered surfactant metabolism.