Possible mechanisms of airway hyperresponsiveness after late asthmatic response in guinea pigs

To elucidate the mechanism of airway hyperresponsiveness after late asthmatic response (LAR), we analyzed bronchoalveolar lavage fluid (BALF) and examined the airway smooth muscle contractility to acetylcholine (ACh). On day 1 after LAR, there was a significant positive correlation between the number of neutrophils in BALF and the increase in airway responsiveness after LAR (r = 0.82, p < 0.01). In the in vitro study, the dose response curve to ACh was significantly shifted to the left after removal of the epithelium in control guinea pigs. However, in hyperresponsive animals after LAR, removal of the epithelium had no significant effect on ACh-induced response. These results indicate that infiltration of neutrophils and other inflammatory cells induce epithelial damage and hence the development of airway hyperresponsiveness after LAR.