2Department of Biochemistry, Iran University of Medical Sciences, Tehran, Iran
Background: Asthma is a chronic inflammatory disease with multifactorial and complicatedmechanisms. Elevated level of exhaled Nitric Oxide (NO) in asthma and other inflammatorylung diseases has led to many studies examining NO as a potential marker of airway inflammation. Objective: This study was designed to determine the level of NO in Bronchoalveolar Lavage(BAL) fluid during early and late stages of asthmatic attack in mouse model. Methods: Inthis study male BALB/c mice were used. The level of NO was determined in BAL fluid ofasthmatic mice five minutes, six and sixteen hours after challenge with methacholine, as irritantand smoke and 5% ovalbumin as allergens, using colorimetric assay. Results: The level of NOincreased upon exposure to all three irritants used in this study (52.3 μM for smoke and 49.5 μ Mfor methacholine) as compared to 22.8 μM for the baseline. Our results showed that NO levels were increased during early phase of asthmatic condition and reached to its maximum level after six hours and decreased at the late stage of asthma (16hrs) possibly by activating a feedback regulatory loop. In addition, high level of NO led to the hypertrophy of smooth muscle that can account for the pathological changes associated with asthma. Conclusion: Thus, NO is an inflammatory marker in asthma and its measurement, as a non-invasive method during asthmatic attack is suggested. A careful development of specific inhibitors for iNOS enzyme during asthmatic attack is also necessary.