Abstract
There is uncertainty regarding the relative importance of chemical mediator release (humoral) and direct physical stimulation of epithelial irritant receptors (neurogenic) in producing exercise induced asthma (EIA). We have approached this question in light of the following: Disodium cromoglycate (DSCG) acts by interfering with the release of mediators from mast cells; histamine by inhalation acts predominantly by stimulating irritant receptors resulting in reflex bronchoconstriction and has only a minor direct effect on bronchial smooth muscle. DSCG effectively blocked EIA in 10/10 asthmatic children but failed to protect 8/8 from the effects of inhaled histamine. We also demonstrated that EIA can be prevented by breathing air at a temperature of 37°c and 100% relative humidity (“steam”) in 8/8 asthmatic children. However, “steam” had no protective effect against inhaled histamine in 6/6 children. We conclude that EIA is due to the release of chemical mediators from bronchial mast cells, rather than by a direct physical effect on the irritant receptors. Moreover, the results with “steam” imply that the stimulus for this release is the cooling and/or drying effect of the inspired air as a result of the hyperventilation occurring during exercise. Once released these mediators, particularly histamine, then presumably induce bronchoconstriction by activating epithelial irritant receptors.
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Mellis, C., Levison, H., Mansell, A. et al. MECHANISM OF EXERCISE INDUCED ASTHMA. Pediatr Res 11, 575 (1977). https://doi.org/10.1203/00006450-197704000-01234
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DOI: https://doi.org/10.1203/00006450-197704000-01234