Am. Surin et al., Simultaneous monitoring of slow cell motility and calcium signals of the guinea pig outer hair cells, HEARING RES, 146(1-2), 2000, pp. 121-133
'Slow' motility (shape changes over seconds to minutes) of the mammalian co
chlear outer hair cell (OHC) could play a protection role from intense soun
d pressure and is associated with elevation of the cytosolic free Ca2+ conc
entration ([Ca2+](i)). In the present work, a new approach was elaborated u
sing fluorescent imaging for continuous monitoring of both [Ca2+](i) change
s and slow motility of OHCs employing the Ca2+ fluorescent indicator Fura-2
. Whole OHC fluorescence and that of cell segments were analyzed to discrim
inate between fluorescence changes caused by [Ca2+](i) rise and those relat
ed to change of the cell shape. The reliability of the method was examined
by simultaneous monitoring of [Ca2+](i) and OHC length changes induced by c
hange of buffer osmolarity or by increase of KCl concentration. The method
revealed that the time course of [Ca2+](i) increase and rate of cell shorte
ning often do not coincide. It was also observed that [Ca2+](i) increased i
n 70 mM KCl more slowly than the rate of KCl delivery to OHCs. The comparis
on of the time courses of [Ca2+](i) elevation, induced by increase of K+/Na
+ ratio and by substitution of Na+ with N-methyl-D-glucamine(+), indicated
that the relatively slow kinetics of [Ca2+](i) increase in the OHC is parti
ally attributed to regulation of Ca2+ homeostasis by the Na+/Ca2+ exchanger
. (C) 2000 Elsevier Science B.V. All rights reserved.