Ford P, Rivarola V, Kierbel A, Chara O, Blot-Chabaud M, Farman N, Parisi M, Capurro C
Laboratorio de Biomembranas, Depto de Fisiología, Facultad de Medicina, Univ. de Buenos Aires, Paraguay 2155, Piso 7, 1121 Buenos Aires, Argentina.
J Membr Biol. 2002 Nov 15;190(2):117-25. doi: 10.1007/s00232-002-1030-8.
The Na+/H+ exchanger (NHE) constitutes a gene family containing several isoforms that display different membrane localization and are involved in specialized functions. Although basolateral NHE-1 activity was described in the cortical collecting duct (CCD), the localization and function of other NHE isoforms is not yet clear, This study examines the expression, localization, and regulation of NHE isoforms in a rat cortical collecting duct cell line (RCCD1) that has previously been shown to be a good model of CCD cells. Present studies demonstrate the presence of NHE-1 and NHE-2 isoforms, but not NHE-3 and NHE-4, in RCCD1 cells. Cell monolayers, grown on permeable filters, were placed on special holders allowing independent access to apical and basolateral compartments. Intracellular pH (pHi) regulation was spectrofluorometrically studied in basal conditions and after stimulation by NH4Cl acid load or by a hyperosmotic shock. In order to differentiate the roles of NHE-1 and NHE-2, we have used HOE-694, an inhibitor more selective for NHE-1 than for NHE-2. The results obtained strongly suggest that NHE-1 and NHE-2 are expressed in the basolateral membrane but that they have different roles: NHE-1 is responsible for pHi recovery after an acid load and NHE-2 is mainly involved in steady-state pHi and cell volume regulation.
钠/氢交换体（NHE）构成一个基因家族，包含几种亚型，这些亚型表现出不同的膜定位并参与特定功能。尽管在皮质集合管（CCD）中描述了基底外侧NHE-1的活性，但其他NHE亚型的定位和功能尚不清楚。本研究检测了大鼠皮质集合管细胞系（RCCD1）中NHE亚型的表达、定位和调节，该细胞系先前已被证明是CCD细胞的良好模型。目前的研究表明，RCCD1细胞中存在NHE-1和NHE-2亚型，但不存在NHE-3和NHE-4。在可渗透滤膜上生长的细胞单层被放置在特殊的支架上，以便独立进入顶端和基底外侧区室。在基础条件下以及在氯化铵酸负荷或高渗休克刺激后，用荧光分光光度法研究细胞内pH（pHi）调节。为了区分NHE-1和NHE-2的作用，我们使用了HOE-694，一种对NHE-1比对NHE-2更具选择性的抑制剂。获得的结果强烈表明，NHE-1和NHE-2在基底外侧膜中表达，但它们具有不同的作用：NHE-1负责酸负荷后pHi的恢复，而NHE-2主要参与稳态pHi和细胞体积调节。
