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.