Microelectrode assessment of chloride-conductive properties of cortical collecting duct.
Microelectrode assessment of chloride-conductive properties of cortical collecting duct.
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DOI：
10.1152/ajprenal.1984.247.2.f291
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发表时间：
1984-08
期刊：
影响因子：
--
通讯作者：
S. Sansom;Edward J. Weinman;Roger G. O'Neil
中科院分区：
文献类型：
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作者：
S. Sansom;Edward J. Weinman;Roger G. O'Neil
采用微电极技术评估离体兔皮质集合管的氯离子传导特性。连续监测跨上皮、顶端和基底外侧膜电位差 Vte、Va 和 Vb，同时定期测量跨上皮电导 Gte 和分数电阻 fRa（顶端与顶端加基底外侧膜电阻的比率）。在所有实验中，通过在不含 HCO3 的溶液中管腔添加 50 µM 阿米洛利，消除了主动转运。降低浴液中的氯离子活性（葡萄糖酸替代）后，Vb 显着去极化，Gte 和 fRa 降低，表明基底外侧膜电导对浴液氯离子活性的主要依赖性。然而，由于提高浴液 K+ 浓度导致 Gte 和 fRa 增加以及 Vb 去极化，因此该势垒处的 K+ 电导也很明显。降低灌注液的氯离子活性会导致 Gte 持续降低，但 fRa 不会降低，其影响与紧密连接的高 C1-电导和顶膜 C1-电导（如果有的话）相一致。通过使用 C1 依赖性电导，估计紧密连接 PtiC1 的平衡时 C1 渗透率接近 1.0 X 10(-5) cm X s-1，基底外侧细胞膜 PbC1 的 C1 渗透率接近 5 X 10(-5) cm X s-1。结论是细胞旁途径提供了跨上皮C1-转运的主要途径。此外，由于同位素测量的 C1- 渗透性比 PtiC1 大几倍，因此必须存在显着的 C1- 跨细胞通量，这意味着顶端细胞膜处的中性交换机制与高基底外侧膜 C1- 电导串联。
The chloride-conductive properties of the isolated rabbit cortical collecting duct were assessed with microelectrode techniques. The transepithelial, apical, and basolateral membrane potential differences, Vte, Va, and Vb, respectively, were monitored continuously along with periodic measurements of the transepithelial conductance, Gte, and fractional resistance, fRa (ratio of apical to apical plus basolateral membrane resistance). Active transport was eliminated in all experiments by luminal addition of 50 microM amiloride in HCO3-free solutions. Upon reducing the chloride activity in the bath (gluconate replacement), there was a marked depolarization of Vb and decrease in Gte and fRa, demonstrating a major dependence of the basolateral membrane conductance on the bath chloride activity. However, a significant K+ conductance at that barrier was also apparent since raising the bath K+ concentration caused an increase in Gte and fRa and depolarization of Vb. Lowering the chloride activity of the perfusate caused a consistent decrease of Gte but not of fRa, effects consistent with a high C1- conductance of the tight junction and little, if any, apical membrane C1- conductance. By use of the C1- -dependent conductances, the C1- permeabilities at equilibrium were estimated to be near 1.0 X 10(-5) cm X s-1 for the tight junction, PtiC1, and 5 X 10(-5) cm X s-1 for the basolateral cell membrane, PbC1. It is concluded that the paracellular pathway provides a major route for transepithelial C1- transport. Furthermore, since the isotopically measured C1- permeability is severalfold greater than PtiC1, a significant transcellular flux of C1- must exist, implicating a neutral exchange mechanism at the apical cell membrane in series with the high basolateral membrane C1- conductance.