Airway Obstruction after Acute Ozone Exposure in BALB/c Mice Using Barometric Plethysmography

BACKGROUND: Airway responsiveness after acute inhalation of ozone is related to the concentration and duration of ozone exposure. Using barometric whole-body plethysmography and increase in enhanced pause (P(enh)) as an index of airway obstruction, we measured the response of BALB/c mice to acute ozone inhalation to study the time course change of pulmonary function after ozone exposure. METHODS: P(enh) was measured before and after exposure to filtered air or 0.12, 0.5, 1, or 2 ppm ozone for 3 hr (n=6/group). In addition, P(enh) was measured 24, 48 and 72 hr after ozone exposure. Bronchoalveolar lavage (BAL) and histopathologic examinations were performed. RESULTS: The increase in P(enh) after ozone exposure was significantly higher in the 0.12, 0.5, 1 and 2 ppm groups compared with the control group (all p<0.01). Increases in P(enh) 24 hr after ozone exposure were significantly lower than those immediately after acute ozone exposure; however, increases in P(enh) 72 hr after ozone exposure were significantly higher than those in the control group (each p<0.01). The proportion of neutrophils in BAL fluid was significantly higher in the group exposed to 2 ppm ozone than in the groups exposed to filtered air or 0.12 ppm ozone (both p<0.01). CONCLUSION: These results indicate that airway obstruction is induced following ozone exposure in a concentration-dependent manner and persists for at least 72 hr.