[Experimental data on epithelial factors modulating bronchial reactivity].

A tracheobronchial smooth muscle reactivity study on isolated guinea pig tracheal rings was done. The presence of two different factors active on smooth muscle, an inhibiting one, as well as an activating one was identified. Generated on different pathways, the epithelial derived relaxing factor is a cyclooxygenase dependent prostaglandin, while the activating epithelial factor seems to be a thromboxane derivate.