Ja. Lopezescamez et J. Schacht, MECHANICALLY INDUCED CALCIUM INCREASES IN ISOLATED VESTIBULAR HAIR-CELLS OF THE GUINEA-PIG, Acta oto-laryngologica, 115(6), 1995, pp. 759-764
Intracellular Ca2+([Ca2+](i)) is elevated by depolarization or mechani
cal stimulation in some hair cell systems. It is not clear whether bot
h these stimuli promote Ca2+ entry in mammalian vestibular hair cells.
We monitored [Ca2+](i) with the indicator fluo-3 in isolated type I v
estibular hair cells of the guinea pig maintained in Hanks' balanced s
alt solution (HBSS). Mechanical stimulation by bolus application of HB
SS led to an immediate rise of [Ca2+](i). The effect depended upon the
presence of extracellular Ca2+ ([Ca2+](0),) and no increase occurred
in calcium-free HBSS supplemented with calcium-chelators. When the cel
ls were depolarized by bolus application of KCl (final concentration,
100 mM KCI in modified HBSS), the increase in [Ca2+](i) was similar to
that elicited by HBSS. In the absence of [Ca2+](0), the application o
f KCl/HBSS led to a slow sustained increase in the fluorescence of the
cells suggesting release of calcium from intracellular stores. Finall
y, treatment of cells with BAPTA prior to mechanical stimulation preve
nted the rise in [Ca2+](i) indicating the need for intact stereociliar
y tip-links. The results are consistent with the hypothesis that mecha
nical stimulation elevates [Ca2+](i) in isolated vestibular hair cells
via calcium influx through mechanotransduction channels.