Breathing and pulmonary surfactant function in mice 24 h after ozone exposure

The aim of this study was to determine whether an acute ozone exposure affects breathing, and the ability of pulmonary surfactant to maintain the patency of terminal conducting airways. BALB/c mice were exposed to ozone (1 part per million (ppm)) for 2, 4, 6, and 8 h. They were examined with plethysmography and with bronchoalveolar lavage (BAL) 24 h later. The BAL fluid was analysed for the presence of inflammatory cells and concentrations of proteins and phospholipids. Surfactant in the remaining BAL fluid was concentrated five-times and examined with a capillary surfactometer (CS). The surfactant was then washed with a large volume of saline solution which was removed following centrifugation. Already, after a 2 h ozone exposure, the respiratory frequency increased from 297+/-6 to 386+/-11 breaths x min(-1) (p<0.0001). Pressure amplitude per breath diminished (p<0.001), indicating a reduced tidal volume. A highly significant surfactant dysfunction was observed with the CS (p<0.0001), although phospholipids increased. However, proteins also increased (p<0.0001) and they or other water-soluble inhibitors apparently caused the surfactant dysfunction since, when they were removed with a washing procedure, the surfactant's normal ability to maintain patency was restored. The acute ozone exposure affected breathing and caused an airway inflammation. The inflammatory proteins or other water-soluble inhibitors reduced the surfactant's ability to secure airway patency.