EFFECT OF THYMOXAMINE AND CROMOLYN SODIUM ON POSTEXERCISE BRONCHOCONSTRICTION IN ASTHMA

[摘要] Of the 22 patients with extrinsic bronchial asthma, 13 patients developed postexercise bronchoconstriction after treadmill exercise, whereas in 9 patients treadmill exercise had no effect on the ventilatory capacity. No statistical difference in the resting lung volumes and CO transfer factor was found between the 2 groups. A significant inhibition of postexercise bronchoconstriction was observed in 12 of 13 patients following thymoxamine or cromolyn sodium inhalation. Inhibition of postexercise bronchoconstriction by .alpha. blockade with thymoxamine suggests that increased .alpha. adrenergic activity in the presence of diminished .beta. receptor function could be the mechanism of postexercise bronchoconstriction in these patients. In asthmatic patients who show diminished .beta. receptor responsiveness to catecholamines, norepinephrine released during exercise could have a marked .alpha. agonistic effect giving rise to bronchoconstriction. Cromolyn sodium has a cyclic phosphodiesterase inhibiting action. This might increase levels of AMP and restore the .beta. receptor responsiveness to catecholamines.