Atp activates a cation conductance and a ca2+-dependent chloride
conductance in hensen cells of the guinea-pig cochlea.
Sugasawa, Masashi, Carlos Erostegui, Christophe Blanchet, and Didier
Dulon.
Laboratoire d'Audiologie Exp[acute]erimentale, Inserm et
Universit[acute]e de Bordeaux II, H[circumflex]opital Pellegrin,
33076 Bordeaux, France
APStracts 3:0209C, 1996.
Simultaneous whole-cell patch clamp and indo-1 fluorescence
measurements were used to characterize ATP-evoked membrane currents
and intracellular Ca2+ ([Ca2+]i) changes in isolated Hensen cells of
the guinea-pig organ of Corti. At negative holding potential, ATP
activated a biphasic inward current and a concomitant increase in
[Ca2+]i. The initial current activated within less than 50 ms, showed
a reversal potential near 0 mV and was reversibly inhibited by 30
[mu]M suramin, suggesting this conductance was mediated by ATP-gated
non-selective cation channels. The delayed ATP-activated current was
mainly carried by Cl- ions as indicated by its shift in reversal
potential when replacing intracellular chloride by gluconate. This
Cl- conductance appeared to be Ca2+-activated secondarily to Ca2+
influx since it required the presence of extracellular Ca2+ and was
suppressed when using an intracellular solution containing 10 mM
BAPTA. In the absence of extracellular Ca2+, ATP still increased
[Ca2+]i concomitant with a monophasic inward cation current,
indicating Ca2+ release from intracellular stores. We conclude that
Hensen cells have ionotropic and metabotropic P2 receptors. They also
have Ca2+-activated Cl- channels which can be activated by
extracellular ATP, suggesting that purinergic receptors in Hensen
cells could play a regulatory role in ion and water balance of
cochlear fluids.
Received 22 January 1996; accepted in final form 17 June 1996.
APS Manuscript Number C44-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96