Section 9
Chapter 8,905

Intracellular calcium variations evoked by mechanical stimulation of mammalian isolated vestibular type I hair cells

Chabbert, C.; Geleoc, G.; Lehouelleur, J.; Sans, A.

Pflugers Archiv European Journal of Physiology 427(1-2): 162-168


ISSN/ISBN: 0031-6768
PMID: 8058466
DOI: 10.1007/bf00585956
Accession: 008904703

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The variations of intracellular free calcium concentration ((Ca-2+)-i) were recorded on-line from guinea-pig isolated vestibular sensory cells using a fura-2 fast fluorescent photometry system, during mechanical displacements of the hair bundle. Repetitive displacements of the hair bundle towards the kinocilium (positive stimulation 7 degree , 300 ms, 2Hz for 10s), revealed (Ca-2+)-i variations detectable only in the cuticular plate. (Ca-2+)-i increased from 105 to 145 nM. Single mechanical displacements of the hair bundle (7 degree , 200 ms, 0.5 Hz) evoked increases of (Ca-2+)-i from 50 +- 23 nM to 139 +- 79 (n = 12). In the opposite direction, the mechanical stimulations (8 degree , 400 ms, 0.5Hz) evoked a decrease of (Ca-2+)-i from 68 +- 17 nM to 37 +- 12 nM (n = 8). The variations of (Ca-2+)-i detected in the cuticular plate during positive displacements of the hair bundle were reversibly abolished in the presence of 100 mu-M gentamicin and they could not be evoked in 0.1 mM calcium in the external medium. From these experiments, it has been concluded that the (Ca-2+)-i variations recorded in the cuticular plate were due to a limited entry of calcium ions through transduction channels localized in the hair bundle. The typical kinetics of variations of (Ca-2+)-i evoked during positive displacements of the hair bundle should account for the presence of strong calcium regulation systems in the hair bundle and cuticular plate.

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