Institute of Aging Research, Key Laboratory for Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical College, Dongguan 523808, China.
J Membr Biol. 2012 Feb;245(2):107-15. doi: 10.1007/s00232-012-9419-5. Epub 2012 Feb 21.
Volume-activated chloride channels have been studied by us extensively in human nasopharyngeal carcinoma cells. However, the chloride channels in the counterpart of the carcinoma cells have not been investigated. In this study, volume-activated chloride currents (I(cl,vol)) were characterized in normal fetal human nasopharyngeal epithelial cells using the whole-cell patch-clamp technique. Under isotonic conditions, nasopharyngeal epithelial cells displayed only a weak background current. Exposure to 47% hypotonic solution activated a volume-sensitive current. The reversal potential of the current was close to the calculated equilibrium potential for Cl(-). The peak values of the hypotonicity-activated current at +80 mV ranged from 0.82 to 2.71 nA in 23 cells. Further analysis indicated that the density of the hypotonicity-activated current in most cells (18/23) was smaller than 60 pA/pF. Only five cells presented a current larger than 60 pA/pF. The hypotonicity-activated current was independent of the exogenous ATP. Chloride channel inhibitors ATP, tamoxifen and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), inhibited the current dramatically. The anion permeability of the hypotonicity-activated chloride channels was I(-) > Br(-) > Cl(-) > gluconate. Unexpectedly, in isotonic conditions, ATP (10 mM) activated an inward-rectified current, which had not been observed in the nasopharyngeal carcinoma cells. These results suggest that, under hypotonic challenges, fetal human nasopharyngeal epithelial cells can produce I(cl,vol), which might be involved in cell volume regulation.
我们曾广泛研究过人类鼻咽癌细胞中的容积激活氯离子通道，但尚未研究过癌细胞对应的氯离子通道。在这项研究中，我们使用全细胞膜片钳技术对正常胎儿鼻咽上皮细胞中的容积激活氯离子电流（I（cl，vol））进行了特征描述。在等渗条件下，鼻咽上皮细胞仅显示出微弱的背景电流。暴露于 47%的低渗溶液会激活体积敏感电流。该电流的反转电位接近 Cl(-)的计算平衡电位。在 +80 mV 的 23 个细胞中，低渗激活电流的峰值范围为 0.82 至 2.71 nA。进一步分析表明，大多数细胞（18/23）的低渗激活电流密度小于 60 pA/pF。只有 5 个细胞的电流大于 60 pA/pF。低渗激活电流与外源性 ATP 无关。氯离子通道抑制剂 ATP、他莫昔芬和 5-硝基-2-（3-苯丙基氨基）苯甲酸（NPPB）显著抑制电流。低渗激活氯离子通道的阴离子通透性为 I(-) > Br(-) > Cl(-) > 葡萄糖酸盐。出乎意料的是，在等渗条件下，ATP（10 mM）激活了内向整流电流，而在鼻咽癌细胞中未观察到这种电流。这些结果表明，在低渗挑战下，胎儿鼻咽上皮细胞可以产生 I（cl，vol），这可能参与细胞体积调节。
