it is concluded that challenge by exercise and ish induces asthma by the same mechanism , the protective effect of water vapor is evidence that the events that lead to bronchial smooth muscle contraction begin in the airway lumen , it is the loss of water rather than the loss of heat from the airways that is the primary stimulus to eia and hia , the mechanism by which water loss induces asthma is by increasing the osmolarity of the epithelial fluid , in some subjects with asthma , cooling of the airways enhances the response to water loss , the increase in osmolarity stimulates the production and release of bronchoactive substances from mast cells and epithelial cells , vagal afferent pathways are activated by changes in osmolarity and by the released mediators , and vagal efferent activity may be modified by alpha-adrenoceptor antagonists and scg .
C0004096
asthma
C0012694
scg