AJP - Cell Physiology, Vol 271, Issue 3 C944-C949, Copyright © 1996 by American Physiological Society
Distribution of Ca2+ channels on cochlear outer hair cells revealed by fluorescent dihydropyridines
T. Oshima, K. Ikeda, M. Furukawa, N. Ueda, H. Suzuki and T. Takasaka
Department of Otolaryngology, Tohoku University School of Medicine, Sendai, Japan.
Physiological evidence has shown that cochlear outer hair cells (OHC)
possess L-type voltage-dependent Ca2+ channels through which Ca2+ enters
the OHC during depolarization. Their subcellular distribution has, however,
remained unclear. In this study, the distribution of L-type Ca2+ channels
on the basolateral plasma membrane of OHC has been demonstrated by the use
of a laser scanning confocal microscope (LSCM) and a fluorescent probe
DMBODIPY-DHP. The fluorescent staining pattern on the basolateral wall is
nonuniform, suggesting a heterogeneous distribution of the channels in the
plasma membrane. Direct imaging of intracellular Ca2+ visualized in real
time by means of the LSCM and the fluorescent Ca2+ probe fluo 3 revealed
temporal and spatial integration of Ca2+ movements and Ca2+ channel
distribution. Exposure to high-K+ solution induced heterogeneity in the
subcellular increase in the intracellular Ca2+ concentration. These results
suggest that the heterogeneous distribution of L-type Ca2+ channels on the
basolateral membrane might induce heterogeneous intracellular Ca2+
distribution during electrical activity in the OHC.
