Airway epithelial cells produce mediators that play a role in regulating airway smooth muscle function. This stUdy was designed to examine the effects of eplthellal-derlved products on contraction of airway smooth muscle. Toavoid biochemical and physical changes that may be produced by stripping epithelium from tracheal smooth muscle, we examined the effect of products from pure cultured tracheel epithelial cells on Intact dog tracheal smooth muscle. When bradykinin (10-5 M) was added to dog epithelial cells In culture and the supernatant was added to strips of