Stimulus-response coupling in mammalian ciliated cells. Demonstration of two mechanisms of control for cytosolic [Ca2+]

Changes of cytosolic Ca2+] have been proposed to couple stimulation of ciliary movement, however, quantitative measurements of fluctuations of intracellular free Ca2+] associated with stimulation of ciliated cells have not been investigated. In primary cultures of rabbit oviductal ciliated cells, the stimulation of ciliary activity produced by micromolar concentrations of adenosine triphosphate (ATP) and prostaglandin F2 alpha (PGF2 alpha) was associated with a transient increase of intracellular Ca2+]. Whereas the increase of cytosolic Ca2+] and beat frequency produced by ATP were inhibited by the Ca-channel blocker LaCl3, the rise of cytosolic Ca2+] and frequency of ciliary beat produced by PGF2 alpha was not affected by LaCl3. These results are the first direct demonstration that fluctuations of cytosolic Ca2+] are associated with increased ciliary beat frequency in mammalian epithelial cells. The present findings suggest two different calcium-dependent mechanisms for stimulus-coupling in ciliary epithelium: ATP acting via purinergic receptor coupled to transmembrane influx of Ca2+, and PGF2 alpha acting via receptor-mediated release of intracellular sequestered Ca.