Published ahead of print on October 31, 2002, doi:10.1164/rccm.200204-293OC Am. J. Respir. Crit. Care Med., Volume 167, Number 2, January 2003, 158-163 A more recent version of this article appeared on January 15, 2003
Submitted on April 8, 2002 Increasing doses of inhaled saline ± amiloride: Effect on mucociliary clearance in normalsNamita Sood1*,1 Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Center for Environmental Medicine and Lung Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 2 Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Division of Pulmonary and Critical Care Medicine, Ohio State University, Columbus, OH, USA, 3 Division of Pulmonary and Critical Care Medicine, Ohio State University, Columbus, OH, USA * To whom correspondence should be addressed. E-mail: sood{at}medctr.osu.edu.
Mucociliary clearance is determined by ciliary activity and rheology of airway surface liquid. To test the hypothesis that mucociliary clearance would increase after inhalation of an osmotically active agent that would increase the volume of airway surface liquid, we measured mucociliary clearance in 16 normal subjects following inhalation of varying tonicities of saline alone, and after pretreatment with a Na+ channel blocker (amiloride). Subjects inhaled vehicle (0.12% saline) or amiloride, followed by inhalation of 0.12% or 0.9% or 7% saline. Subsequently, mucociliary clearance rates were measured by gamma scintigraphy of inhaled 99mTc Fe2O3. Mucociliary clearance of whole and peripheral lung was increased (~2-fold) after inhalation of increasing concentrations of saline (p<0.04.). Pretreatment with amiloride increased mucociliary clearance rates (~2-fold) after inhalation of 0.12% and 0.9% saline (p<0.05), but not 7% saline. The rates of mucociliary clearance by pretreatment with amiloride, and 7% saline, alone (~1.4% per min) approached the rapid mucociliary clearance rates (~2.0% per min) reported in systemic pseudohypoaldosteronism, which has loss-of-function mutations of the epithelial Na+ channel and an increased volume of airway surface liquid. We conclude that maneuvers that increase the volume of airway surface liquid are associated with increased rates of mucociliary clearance in normal subjects. Key words: Mucociliary clearance, airway surface liquid, epithelial Na+ channel, aerosolized NaCl
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