Effect of APC on airway hyperresponsiveness. (A) Inhalation of APC before exposure to OVA was associated with significantly lower Penh values in the OVA + APC group than in the OVA + SAL group after increasing concentrations of methacholine; this difference between these 2 groups of animals was significant after inhalation of 6, 12, and 24 mg/mL methacholine. Penh values in the APC or SAL group were not significantly different from those measured in the OVA + APC group at any concentration of methacholine. In the experiment in which treatment with APC was done after OVA inhalation, the Penh values in the OVA + APC group was significantly different from those measured in the OVA + SAL group after inhalation of 24 mg/mL methacholine (B). Penh values in the APC or SAL group were not significantly different from those measured in the OVA + APC group during inhalation of 24 mg/mL methacholine. Data represent the mean ± SD of values obtained in 6 mice. *P < .05 and ¶P < .05, compared with other groups.