Effect of Ca2+ on the ciliary beat frequency of skinned dog tracheal epithelium

Beat frequency of dog tracheal ciliated epithelium was measured using a profile projector and a photomultiplier. The preparation, treated with 50 micrograms/ml of saponin for 15 min, lost osmotic behavior and the ciliary beat came to depend on externally applied MgATP2- indicating that ciliated epithelium is skinned with saponin. Beat frequency of skinned cilia did not increase with Ca2+ in 0.1 mM MgATP2- with no ATP-regenerating system. Under 4 mM Mg ATP2- the beat frequency increased with an increase in Ca2+ from 0.3 to 10 microM, although a marked beat continued in the virtual absence of Ca2+ sensitivity and maximum beat frequency increased with the addition of 2.4 microM calmodulin. The effect of calmodulin inhibitor (W-7) on skinned preparations was somewhat weaker than that on intact ones. We concluded that Ca2+, within the physiological range of concentrations, directly activated the ciliary proteins and increased the ciliary beat frequency. The addition of calmodulin augments the effect of Ca2+ but the basal beat frequency is not Ca2+ dependent.