The obligatory role of calcium in the development of antigen-induced airway hyperreactivity to cold provocation in the rat isolated trachea.

The effect of antigen challenge on cold provocation (30-10 degrees C) in isolated tracheal segments from control (normal) and ovalbumin-sensitized rats was studied. Sensitization alone or acute cold provocation (10 degrees C) alone was not sufficient to cause contraction of tracheal smooth muscle preparation. Following recovery from antigen-induced responses (Schultz-Dale phenomenon) in sensitized rat segments, cold provocation induced strong contractile responses. Both the antigen-induced contractions and the subsequent development of airway hyperreactivity to cold were dependent on extracellular Ca2+ and inhibited by verapamil. The data in this study indicate that extracellular Ca2+ plays an obligatory role in the mediation of antigen-induced contractile responses as well as the subsequent development of hyperreactivity to cold provocation in rat tracheal smooth muscle.