Na+ transport and impedance properties of cultured renal (A6 and 2F3) epithelia.
Na+ transport and impedance properties of cultured renal (A6 and 2F3) epithelia.
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培养的肾（A6 和 2F3）上皮细胞的 Na 转运和阻抗特性。
DOI：
10.1007/bf00236439
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Clausen,C
中科院分区：
文献类型：
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作者：
Wills,NK;Purcell,RK;Clausen,C
以前对完整上皮的阻抗分析研究因结缔组织或平滑肌的存在而变得复杂。我们现在报告这一方法首次应用于培养上皮单分子层。阻抗分析是一种无损的方法，用于推导肾细胞系A6及其亚克隆细胞系2F3生长的上皮细胞的定量形态计量学参数。亚克隆性2F3细胞系因其固有的较高的Na+转运速率而被选为与A6细胞的比较。2F3上皮细胞对阿米洛利敏感的短路电流明显高于A6上皮细胞(分别为44±2和27±2μA/cm~2)。然而，由于细胞(GC)和细胞旁(GJ)电导的相互差异，两种上皮的跨皮电导(GT)相似(2F3为0.62±0.04ms/cm2，A6为0.57±0.04ms/cm2)。2F3的Gj明显低于A6(Gj=0.23±0.02)，Gc值明显高于A6(Gj=0.33±0.04ms/cm2和Gc=0.39±0.16和0.26±0.10ms/cm2)。然而，在开路条件下，两种上皮细胞的Na+转运驱动力(EC)和跨细胞Na+电流的量是相似的。三种不同的基于形态的等效电路模型被用来评估上皮细胞的阻抗特性：一种是分布式模型，它考虑了细胞间间隙的侧向阻力；另两种模型(“双层”和“通路阻力”模型)，它修正了基底膜向底层过滤器支撑物中充满液体的小突起的阻抗。虽然数据可以用分布模型来拟合，但根尖/基底侧膜阻力之比的估计值太大了。相比之下，其他模型提供了统计上更好的拟合和对膜阻力比的合理估计。双层模型和接触阻力模型也提供了对根尖和基底侧膜电导和电容的类似估计。此外，这两个模型都提供了有关基底侧向凸起的电导率和面积的新信息。2F3的根尖膜电导(0.79±0.23ms/cm~2)显著高于A6上皮(0.37±0.07ms/cm~2)，但顶膜电容(2F3和A6分别为1.4±0.04和1.2±0.1μF/cm~2)和基底膜电导(3.48±1.67和2.95±0.40ms/cm~2)无显著差异。两种上皮细胞在开放条件下的跨细胞Na+电流具有可比性，这可能是两种上皮细胞基侧膜特性相似的原因。我们认为，阻抗分析可以作为一种非常有用的、无创的方法来推断培养上皮单层的膜特性。A6和2F3细胞在顶膜Na+电导和细胞旁电导方面的差异可能为评估Na+转运和紧密连接蛋白的调节提供有用的工具。
Previous impedance analysis studies of intact epithelia have been complicated by the presence of connective tissue or smooth muscle. We now report the first application of this method to cultured epithelial monolayers. Impedance analysis was used as a nondestructive method for deducing quantitative morphometric parameters for epithelia grown from the renal cell line A6, and its subclonal cell line 2F3.The subclonal 2F3 cell line was chosen for comparison to A6 because of its inherently higher Na+transport rate. In agreement with previous results, 2F3 epithelia showed significantly higher amiloride-sensitive short-circuit currents (Isc) than A6 epithelia (44±2 and 27±2μA/cm2, respectively). However, transepithelial conductances (GT) were similar for the two epithelia (0.62±0.04 mS/cm2for 2F3 and 0.57±0.04 mS/cm2for A6) because of reciprocal differences in cellular (Gc) and paracellular (Gj) conductances. Significantly lowerGjand higherGcvalues were observed for 2F3 epithelia than A6 (Gj= 0.23±0.02 and 0.33±0.04 mS/ cm2andGc= 0.39±0.16 and 0.26±0.10 mS/cm2, respectively). Nonetheless, the cellular driving force for Na+transport (Ec) and the amount of transcellular Na+current under open-circuit conditions (Ic) were similar for the two epithelia.Three different morphologically-based equivalent circuit models were derived to assess epithelial impedance properties: a distributed model which takes into account the resistance of the lateral intercellular space and two models (the “dual-layer” and “access resistance” models), which corrected for impedance of small fluid-filled projections of the basal membrane into the underlying filter support. Although the data could be fitted by the distributed model, the estimated value for the ratio of apical to basolateral membrane resistances was unreasonably large. In contrast, the other models provided statistically superior fits and reasonable estimates of the membrane resistance ratio. The dual-layer model and access resistance models also provided similar estimates of apical and basolateral membrane conductances and capacitances. In addition, both models provided new information concerning the conductance and area of the basolateral protrusions. Estimates of the apical membrane conductance were significantly higher for 2F3 (0.79±0.23 mS/cm2) than A6 epithelia (0.37±0.07 mS/cm2), but no significant difference could be detected for apical membrane capacitances (1.4±0.04 and 1.2±0.1μF/cm2for 2F3 and A6, respectively) or basolateral membrane conductances (3.48±1.67 and 2.95±0.40 mS/cm2). The similar basolateral membrane properties for the two epithelia may be explained by their comparable transcellular Na+currents under open-circuit conditions.We conclude that impedance analysis can be a highly useful and noninvasive method for deducing the membrane properties of cultured epithelial monolayers. The difference between A6 and 2F3 epithelia with respect to apical membrane Na+conductance and paracellular conductance may provide a useful tool for assessing the regulation of Na+transport and tight junctional proteins.