Nonselective cation and Cl channels in luminal membrane of the marginal cell.
Single-channel currents of the luminal membrane of marginal cells dissected from the guinea pig cochlea were investigated using the patch-clamp technique. Nonselective cation channels having a linear conductance of 27 pS were activated by depolarization, cytoplasmic Ca2+, and cytoplasmic acidification. Cytoplasmic ATP inactivated the channel. A mixture of 3-isobutyl-1-methylxanthine and forskolin activated a small-conductance Cl channel in the cell-attached mode. On excision in the inside-out mode, the Cl channel was inactivated, but it was reactivated by a cytoplasmic catalytic subunit of protein kinase A with ATP. This Cl channel had a linear conductance of 12 pS, and its activity was little affected by voltage. The sequence of permeation by anions was Br- > Cl > I-. The Cl channel blocker diphenylamine-2-carboxylic acid (3 mM) completely blocked the channel, but 5-nitro-2-(3-phenylpropylamino)-benzoic acid (50 microM) blocked it only partially. The above-mentioned characteristics are similar to those of the well-demonstrated Cl- channel, cystic fibrosis transmembrane regulator.
Sunose
H
H
Department of Otolaryngology, Tohoku University School of Medicine, Sendai, Japan.
Ikeda
K
K
Saito
Y
Y
Nishiyama
A
A
Takasaka
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002412:Cations / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D018118:Chloride Channels; D003051:Cochlea / Q000166:cytology / Q000378:metabolism*; D004553:Electric Conductivity; D006168:Guinea Pigs; D007473:Ion Channels / Q000378:metabolism* / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology
D002412:Cations; D018118:Chloride Channels; D007473:Ion Channels; D008565:Membrane Proteins; D000255:Adenosine Triphosphate