Regulation of airway ciliary activity by Ca2+: simultaneous measurement of beat frequency and intracellular Ca2+.
Airway ciliary activity is influenced by [Ca2+]i, but this mechanism is not fully understood. To investigate this relationship, ciliary activity and [Ca2+]i were measured simultaneously from airway epithelial ciliated cells. Ciliary beat frequency was determined, for each beat cycle, with phase-contrast optics and high-speed video imaging (at 240 images s-1) and correlated with [Ca2+]i determined, at the ciliary base, by fast imaging (30 images s-1) of fura-2 fluorescence. As a mechanically induced intercellular Ca2+ wave propagated through adjacent cells, [Ca2+]i was elevated from a baseline concentration of 45 to 100 nM, to a peak level of up to 650 nM. When the Ca2+ wave reached the ciliary base, the beat frequency rapidly increased, within a few beat cycles, from a basal rate of 6.4 to 11.6 Hz at 20-23 degrees C, and from 17.2 to 26.7 Hz at 37 degrees C. Changes in [Ca2+]i, above 350 nM, had no effect on the maximum beat frequency. We suggest that airway ciliary beat frequency is 1) controlled by a low range of [Ca2+]i acting directly at an axonemal site at the ciliary base and 2) that a maximum frequency is induced by a change in [Ca2+]i of approximately 250-300 nM.
Lansley
A B
AB
Department of Pharmacy, King's College London, London SW3 6LX, England.
Sanderson
M J
MJ
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D002923:Cilia / Q000187:drug effects* / Q000378:metabolism; D005453:Fluorescence; D016257:Fura-2; D008858:Microscopy, Phase-Contrast / Q000295:instrumentation; D018715:Microscopy, Video / Q000295:instrumentation; D010507:Periodicity; D011817:Rabbits; D013314:Stress, Mechanical; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D002118:Calcium; D016257:Fura-2