Ion channels in basolateral membrane of marginal cells dissociated from gerbil stria vascularis

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• 作者：Takeuchi ; Shunji ; Ando ; Motonori ; Kozakura ; Kenichi ; Saito ; Haruo ; Irimajiri ; Akihiko
• 关键词：Marginal cell ; Ion transport ; Nonselective cation channel ; Cl^&minus ; channel
• 刊名：Hearing Research
• 出版年：1995
• 期刊代码：111_03785955
• 类别：med
• 出版时间：March, 1995
• 卷：83
• 期：1-2
• 页码：89-100
• 文件大小：1.54 M

摘要

The basolateral membrane of isolated strial marginal cells has been probed for conductive pathways by the patch-clamp technique. Two types of voltage-insensitive channels were identified in both cell-attached and excised patches. Of these, frequently (69%of excised patches) observed was a Ca²⁺-activated nonselective cation channel having a unit conductance of 24.9 ± 0.5 pS (N = 16). Other characteristics of this type in excised patches include: 1) linear I-V relations with (bath), 2) a permeability sequence of NH⁺₄ > Na⁺ = K⁺ = Rb⁺ > Li⁺, 3) a flickering block by quinine or quinidine (both 1 mM), and 4) a dose dependent block of its activity by ADP or ATP ( = 20-35), both from the cytosolic side. Channels with similar characteristics were found in the apical membrane of the same cell; however, the basolateral channels were 2-4 times more densely distributed than the apical counterparts. Also frequently (57%) detected was a Cl⁻ channel of 80.0 ± 0.5 pS (N = 6), whose activity was Ca²⁺ independent. Additionally, this Cl⁻ channel had: 1) linear I-V relations with symmetric Cl⁻, 2) a permeability sequence of Cl⁻ > Br⁻ > I⁻ ≥ NO⁻₃ ≥ gluconate⁻, and 3) a complete and reversible block by 1 mM diphenylamine-2-carboxylate. In contrast to the apical Cl⁻ channels, the basolateral ones had a much higher density (57%vs. < 1%) as well as a higher unit conductance (80 pS vs. 50 pS) than the apical counterpart. The relative abundance of these two types as the major conductive pathways for Na⁺, K⁺, and Cl⁻ in the basolateral region must be taken into account when addressing the role of strial marginal cells in generating the positive endocochlear potential. The Cl⁻ channel may facilitate Cl⁻ distribution across the basolateral membrane.