Animal models of asthma and chronic bronchitis

Human asthma is characterized by three critical phenotypic traits: intermit tent reversible airway obstruction, airway hyperresponsiveness and airway i nflammation. In animal models of asthma, airway hyperresponsiveness is an i mportant feature. This trait is characterized by an exaggerated bronchocons trictor response that would have little physiological consequence in an oth erwise unaffected or normal individual. In this article we explore two dist inct facets of airway responsiveness. The first is the genetic basis for va riations in airway responsiveness that occur in mice in the absence of any specific environmental manipulation. We demonstrate that standard generic a pproaches can be successfully applied to the identification of regions of t he mouse genome linked to the expression of airway hyperresponsiveensss The second topic addressed in this review is the change in airway responsivene ss induced in rats by repeated exposure to sulphur dioxide gas. With daily exposure to high concentrations of sulphur dioxide gas, there is chronic in jury and repair of epithelial cells. Over time, rats develop mucous hyperse cretion. airway inflammation, increased airway resistance and airway hyperr esponsiveness. This model has provided useful information on the mechanisms underlying the pathophysiological events that typify the chronic bronchiti s in humans.