The respiratory epithelium releases a smooth muscle relaxing factor

Abstract

Dysfunction of respiratory epithelial cells may contribute to the pathogenesis of bronchial hyperreactivity in asthma. The aim of this study was to determine whether the respiratory epithelium can modulate directly the responsiveness of bronchial smooth muscle. The results indicate that the respiratory epithelium releases a smooth muscle relaxing factor to inhibit the effects of bronchoconstrictor agonists and to augment the direct inhibitory effects of relaxing stimuli. Moreover, the influence of epithelium removal on the responses to nerve stimulation suggests that this inhibitory factor might be released following activation of the epithelium by these agonists. For example, the delay in the epithelium-dependent inhibitory response during nerve stimulation might represent the diffusion of nerve-released acetylcholine to the epithelial cells.