Effect of antigen challenge on sensitized guinea pig trachea.

Isolated tracheal preparations (ITP) were obtained from control guinea pigs and animals with acute and chronic experimental asthma (AA and CHA). It was observed that after in vitro antigen challenge, in addition to the classic Schultz-Dale response (the immediate increase in the tone of sensitized airway smooth muscle), a significant increase of the active state of airway smooth muscle was seen. This active state was observed as the potentiated, phasic, mechanical activities of ITP and was evaluated by both maximum active tension (AT max) and maximum rate of tension development (dT/dt). No apparent functional differences in the tonic response or the active state of airway smooth muscle between AA and CHA animals were found. Tracheas isolated from animals with CHA demonstrated smooth muscle hypertrophy as measured by wet, dry and relative weights of the tracheas. The repeated administration of antigen into the experimental bath was ineffective in inducing any physiological changes. The administration of histamine to ITP from control animals induced changes of mechanical activities of trachea comparable to those seen in both AA and CHA animals.