Relationship between airway inflammation and bronchial hyperreactivity in rats and the effect of theophylline

AIM: To determine the relationship between antigen-induced airway inflammation characterized by pulmonary eosinophilia and bronchial hyperreactivity in rats, and to evaluate the effect of theophylline at different doses. METHODS: In ovalbumin (OA)-sensitized rats, bronchiole wall area, eosinophils around bronchi, and the responses to methacholine (MCh) aerosol were measured after 1% OA aerosol challenge with computer-assisted techniques. RESULTS: OA challenge caused both inflammation and airway hyperreactivity, and there was a significantly positive correlation between them. Oral theophylline (1-12.5 mg/kg, bid for 7 days) attenuated antigen-induced inflammation (swelling of bronchiole walls and pulmonary eosinophilia) and bronchial hyperreactivity. CONCLUSION: These findings confirm that bronchial hyperreactivity positively correlates to airway inflammation in the rat, and suggest that theophylline at relatively lower doses has anti-inflammatory effect in airway allergic reaction.