Spontaneous oscillation of the ciliary beat frequency regulated by release of Ca from intracellular stores in mouse nasal epithelia.

Ciliary beating frequency (CBF) was investigated in ciliated nasal epithelial cells (cMNECs) isolated from mice using video microscopy equipped with a high-speed camera. In cMNECs, a spontaneous CBF oscillation was observed. The CBF oscillation was abolished by BAPTA-AM but not by Ca-free solution. The addition of thapsigargin, which depletes Ca from internal stores, also abolished CBF oscillation. Moreover, the intracellular Ca concentration [Ca], spontaneously oscillated even with the Ca-free solution. Moreover, 2APB (an inhibitor of the IP receptor) abolished CBF oscillation in cMNECs. Overall, these findings suggest that the CBF oscillation in cMNECs is triggered by the release of Ca from the IP-sensitive internal stores. Moreover, IBMX, an inhibitor of phosphodiesterase, did not affect CBF oscillation in cMNECs, although it slightly increased CBF. These results suggest that CBF oscillations were induced by [Ca] oscillation controlled via the release of Ca from IP-sensitive stores, rather than via cAMP accumulation. CBF oscillation possibly plays a crucial role in maintaining an efficient mucociliary clearance in the nasal epithelia.