BK channels mediate the voltage-dependent outward current in type I spiral ligament fibrocytes
| Autor: | Zhijun Shen, Bradley A. Schulte, Debra J. Hazen-Martin, Fenghe Liang |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Male
BK channel Membrane Potentials Potassium Channels Calcium-Activated chemistry.chemical_compound Cations Potassium Channel Blockers Animals Repolarization Large-Conductance Calcium-Activated Potassium Channels Reversal potential Electrochemical gradient Cells Cultured Membrane potential Ligaments Tetraethylammonium biology Chemistry Osmolar Concentration Electric Conductivity Intracellular Membranes Anatomy Iberiotoxin Sensory Systems Cochlea Potassium Biophysics biology.protein Calcium Female Gerbillinae Peptides Intracellular |
| Zdroj: | Hearing Research. 187:35-43 |
| ISSN: | 0378-5955 |
| Popis: | Recent experimental and clinical studies have provided considerable evidence to support the phenomenon of K(+) recycling in the mammalian cochlea. However, the precise cellular and molecular mechanisms underlying and regulating this process remain only partially understood. Here, we report that cultured type I spiral ligament fibrocytes (SLFs), a major component of the K(+) recycling pathway, have a dominant K(+) membrane conductance that is mediated by BK channels. The averaged half-maximal voltage-dependent membrane potential for the whole-cell currents was 70+/-1.2 mV at 1 nM intracellular free Ca(2+) and shifted to 38+/-0.2 mV at 20 microM intracellular free Ca(2+) (n=4-6). The reversal potential of whole-cell tail currents against different bath K(+) concentrations was 52 mV per decade (n=3-6). The sequence of relative ion permeability of the whole-cell conductance was K(+)Rb(+)z.Gt;Cs(+)Na(+) (n=5-17). The whole-cell currents were inhibited by extracellular tetraethylammonium and iberiotoxin (IbTx) with IC(50) values of 0.07 mM and 0.013 microM, respectively (n=3-7). The membrane potentials of type I SLFs measured with conventional zero-current whole-cell configuration were highly K(+)-selective and sensitive to IbTx (n=4-9). In addition, the BK channels in these cells exhibited voltage-dependent and incomplete inactivation properties and the recovery time was estimated to be approximately 6 s with repetitive voltage pulses from -70 to 80 mV (n=3). These data suggest that BK channels in type I SLFs play a major role in regulating the intracellular electrochemical gradient in the lateral wall syncytium responsible for facilitating the K(+) movement from perilymph to the stria vascularis. |
| Databáze: | OpenAIRE |
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