MODIFICATION OF ALLERGIC BRONCHOCONSTRICTION BY A CALCIUM-ANTAGONIST - MODE OF ACTION

  • 1 January 1983
    • journal article
    • research article
    • Vol. 127  (6) , 675-679
Abstract
Because both degranulation of mast cells and contraction of airway smooth muscle are dependent upon the influx of Ca, a Ca blocking agent might modify allergic bronchoconstriction by at least these 2 mechanisms. Sheep allergic to Ascaris suum antigen were treated with the Ca antagonist Verapamil prior to airway challenge with an aerosol of A. suum antigen and the response was investigated without pretreatment. Aerosolized A. suum antigen increased mean pulmonary resistance (RL) to 530% of baseline (n = 6). Pretreatment with i.v. administered Verapamil (150 .mu.g/kg) increased mean RL to 225% of baseline but bronchoconstriction produced by subsequent antigen challenge was completely prevented. Verapamil did not modify bronchoconstriction produced by aerosols of histamine and carbachol, agents that act upon airway smooth muscle. It did not reverse the increase in RL induced by an i.v. infusion of carbachol. Verapamil, at the dosage used, did not prevent allergic bronchoconstriction by a direct action on smooth muscle and therefore was probably effective by inhibiting the release of mast cell mediators.