The Regulation of Airway Ciliary Beat Frequency by Intracellular Calcium

During breathing, the airways transport into the lungs large quantities of air that is contaminated with a variety of pollutants, particles, and bacteria. To prevent the accumulation of these contaminants, the airways have developed a defense mechanism of mucociliary clearance that relies on ciliary activity (Sanderson, 1997; Wanner et al., 1996). The airways, from the trachea to the terminal bronchi­oles, are lined with a ciliated epithelium. The cilia of each cell project towards the airway lumen and are bathed in a “ watery” ionic solution called the pericili-ary layer (Fig. la). Each cilium performs a repetitive beat cycle consisting of a rest, recovery, and effective stroke. During the effective stroke the cilium makes contact with the overlying mucus and transports it, together with entrapped parti­cles, along the airways for expulsion at the esophagus. * Current affiliation: University of Brighton, Brighton, United Kingdom, f Current affiliation: National Jewish Medical and Research Center, Denver, Colorado.