The functional conversion hypothesis: a contributor to exercise-induced asthma?

Studies on receptor stability suggest that functional conversion of adrenoceptors between alpha and beta can occur in mammalian myocardium due to variations in the environment such as temperature changes, pH or hormonal changes. If adrenoceptors of the respiratory system behave similarly, heat and water loss of airways noted during hyperventilation could lead to functional loss of inhibitory beta and expression of excitatory alpha adrenoceptors. This would have the effect of counter-action of adrenergic homeostatic mechanisms which may be of particular importance in asthmatic subjects. The hypothesis of adrenoceptor interconversion could contribute to the airway obstruction observed during exercise in asthmatics. This concept is supported by scattered reports of the efficacy of alpha adrenergic antagonists in preventing exercise-induced asthma.