The hypothesis that relative movement between respiratory epithelium and surrounding fluid modulates both ciliary activity and mucosal secretion-absorption properties was tested. Fresh human (HM) and bovine sinusal mucosae (BM) were mounted in transparent chambers perfused with defined media at 36 degrees C. The fluid advanced along the ciliated surface at 15-30 microns/s. Transepithelial transport of electrolytes was studied by using voltage-clamp technique. Ciliary beating frequency (CBF) was recorded by using laser reflectometry. Average transmucosal potential difference (apical side negative) and short-circuit current (Isc) were -0.5 mV and 17 microA.cm-2 for HM and -1.4 mV and 28 microA.cm-2 for BM. Average CBF was 900 beats/min. Ionic pathways included basolateral Na,K-ATPase, K+ channels and symports for Na-Cl and Na-glucose, and apical channels for Na+ (absorption) and for Cl- and K+ (secretion). Increase of fluid velocity up to 300 microns/s induced significant increase of both Isc (63%) and CBF (29%). Such adaptations of transepithelial fluid transport and ciliary activity to hydrodynamic conditions might reflect a mechanism of coordination between the secretion of mucus electrolytes and mucociliary clearance.