Corticotropin-releasing factor and adrenocorticotropin stimulate ciliary motility in rabbit tracheal epithelium

To assess the effects of corticotropin-releasing factor (CRF) and adrenocorticotropin (ACTH) on airway ciliary activity, we measured ciliary beat frequency (CBF) by a photoelectric method in response to these peptides in cultured rabbit tracheal explants. When cumulatively added, both CRF and ACTH increased CBF in a dose-dependent fashion. Treatment of tissues with Ca2+-free medium or nifedipine abolished the effect of CRF but not of ACTH. The CRF- and ACTH-induced ciliostimulations were not affected by indomethacin or autonomic antagonists, but were attenuated by nordihydroguaiaretic acid and by their receptor antagonists, alpha-helical CRF (9-41) and ACTH (7-38). Intracellular cyclic AMP levels were significantly increased by CRF and ACTH. These results suggest that CRF and ACTH stimulate airway ciliary motility through the activation of adenylate cyclase and lipoxygenase by binding to their specific receptors, where the effect of CRF may be triggered by Ca2+ influx.