Ozone affects breathing and pulmonary surfactant function in mice

The effect on breathing of BALB/c mice immediately following ozone exposure (2 ppm) for 0, 2, 4, 6, and 8 h was studied with a whole body plethysmograph. Whether such exposure affected the normal function of pulmonary surfactant of maintaining airway patency was evaluated with a capillary surfactometer. Respiratory rate in mice that were not exposed was 358 +/- 16 (mean +/- S.E.) breaths/min and decreased to 202 +/- 10 after 6 h exposure. The mean pressure change caused by breathing diminished significantly, indicating a reduced tidal volume. BAL fluid from controls maintained patency for 88 +/- 2% of the study time; 120 s, implying a good surfactant function, but the ozone exposure caused the surfactant to lose its capability of maintaining patency (P < 0.0001). This decaying surfactant function of the BAL fluid coincided with an increasing protein concentration in the fluid of exposed animals (1.46 +/- 0.14 mg/ml in the 8-h group) as compared to controls (0.44 +/- 0.04 mg/ml, P < 0.0001). It is concluded that leakage of plasma proteins into the airway lumen was probably the main reason for the surfactant dysfunction, which may have contributed to the altered breathing pattern. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.