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.