[Ozone-induced airway hyperresponsiveness in guinea pigs]

We studied the time related changes of airway hyperresponsiveness induced by ozone inhalation (2.9 ppm, 30 min) in guinea pigs. In unanesthetized and spontaneously breathing guinea pigs, the respiratory resistance was measured by a forced oscillation technique. The respiratory resistance and respiratory frequency were unchanged until 24 hours after ozone inhalation. In mechanically ventilated guinea pigs, airway responsiveness to inhaled methacholine was determined using a modification of the Konzett-Rössler technique, and after methacholine challenge bronchoalveolar lavage (BAL) was performed for cell yield. At 1 hour and 3 hours after ozone inhalation, airway responsiveness was increased significantly, but returned to the control level at 6 hours. In the BAL fluid, there was a significant increase in neutrophils at 3 hours after ozone inhalation and thereafter. In the separated groups, before air or ozone inhalation, human serum albumin (HSA) was administered intravenously, and BAL was performed 1 hour after inhalation. In the ozone inhalation group, the concentration of HSA in BALF was increased significantly compared to the air inhalation group. These results suggest that airway hyperresponsiveness induced by ozone inhalation may occur before the influx of neutrophils into the airways and may depend on some structural changes such as submucosal and mucosal edema induced by the enhancement of capillary permeability.