Regulation of Cl- conductance in delayed shortening and shrinkage of outer hair cells.
Tetanic electrical field stimulation induces slow and delayed shortening of isolated outer hair cells (OHCs) from guinea pigs concomitant with a decrease in cell volume and intracellular Cl- concentration ([Cl-]i). These responses are dependent on the entry of Ca2+ and the activation of both Ca(2+)-activated K+ channels and furosemide-sensitive Cl- channels. In this study, the regulatory mechanisms of the Cl- channels of OHCs were investigated. Tetanic stimulation induced shrinkage and a decrease in [Cl-]i, the latter being unrelated to the activity of the Na+/K+/2Cl- cotransporter. These responses were inhibited by tetraethylammonium, and the inhibition was overcome by an increase in the K+ conductance by valinomycin, though valinomycin alone did not affect the resting cell volume and [Cl-]i. The deprivation of extracellular Ca2+ inhibited the stimulation-induced changes in volume and [Cl-]i even in the presence of valinomycin. These results suggest that electrical stimulation-induced delayed shortening and shrinkage of OHCs are induced by Cl- efflux, which is electrically coupled to K+ efflux and independently activated following an increase in intracellular Ca2+ concentration.
Department of Otolaryngology, Kansai Medical University, Osaka, Japan.
S
S
Ohnishi
M
M
Hara
C
C
Inagaki
T
T
Yamashita
T
T
Kumazawa
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology*; D004558:Electric Stimulation; D005110:Extracellular Space / Q000187:drug effects / Q000502:physiology; D005665:Furosemide / Q000494:pharmacology; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000187:drug effects / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D013757:Tetraethylammonium Compounds; D002034:Bumetanide; D014634:Valinomycin; D019789:Tetraethylammonium; D005665:Furosemide