The contribution of mast cells to the late-phase of allergic asthma in rats

Introduction: Mast cells are thought to be the main cause of an immediate asthmatic response, but their contribution to the late-phase of asthma is unknown.Objective: To prove the contribution of preactivated mast cells to the late phase of allergic asthma by advanced activation.Methods: Mast cell function in the late-phase of asthma was studied. Rats (wild, +/+ and mast cell deficient, Ws/Ws) were challenged with OVA to investigate the relationship between the contraction of airways and the population of inflammatory cells in the trachea.Result: During the entire asthmatic period, the contraction of the airway after OVA challenge in +/+ rats was enhanced significantly compared to Ws/Ws rats, especially in the late phase. The bronchoalveolar lavage fluid histamine in +/+, but not Ws/Ws, rats increased 5.3-fold in 30 min and 3.4-fold in 8 h after challenge, significantly. The number of mucosal mast cells in the tracheal epithelial layer in +/+ rats increased significantly 2.2-fold over controls at 8 h after challenge, as demonstrated by in situ hybridization.Conclusions: Mast cells may contribute to the late phase of asthmatic response by continuous mast cell activation and the mucosal mast cell number increased in the late phase of asthmatic response.Received 15 October 2004; returned for revision 21 December 2004; accepted by A. Falus 26 January 2005