Dissociation enzyme effects on the potassium currents of inner hair cells isolated from guinea-pig cochlea.
Tetraethylammonium (TEA)-sensitive potassium currents in the cochlear inner hair cells (IHCs) possess the kinetics of fast inactivation. Some enzymes using for IHCs dissociation affect these inactivation kinetics. IHCs were dissociated from guinea-pig cochlea by 1 mg/ml trypsin or 0.25 mg/ml protease VIII, and the properties of the K+ currents were compared using conventional whole-cell voltage-clamp recordings. TEA-sensitive potassium currents showed fast inactivation kinetics in both trypsin-dissociated cells and protease VIII-dissociated cells. The time constant of the inactivation phase in trypsin-treated cells was similar to that in protease VIII-treated cells. However, the rate of inactivation (compared by the ratio between the steady-state current and initial peak current) in protease VIII-treated cells was larger than that in trypsin-treated cells. In protease VIII-dissociated cells, the time constant of recovery from inactivation elucidated by paired-pulse protocol was 3.5 ms. Papain is another enzyme that is sometimes used for dissociating IHCs, so effects of papain were observed. Extracellular papain application (8 unit/ml) demonstrated a slight increase of the outward potassium currents.
Kimitsuki
Takashi
T
Department of Otorhinolaryngology, Miyazaki Medical College, University of Miyazaki, 5200 Kihara, Miyazaki-Gun 889-1692, Japan. kimituki@fc.med.miyazaki-u.ac.jp
Ohashi
Mitsuru
M
Wada
Yuki
Y
Fukudome
Shinji
S
Komune
Shizuo
S
D000818:Animals; D003051:Cochlea / Q000378:metabolism; D004553:Electric Conductivity; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials; D010206:Papain / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019789:Tetraethylammonium / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism
D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D019789:Tetraethylammonium; D010447:Peptide Hydrolases; D014357:Trypsin; D010206:Papain