Hayslett J P, Gögelein H, Kunzelmann K, Greger R
Max-Planck-Institut für Biophysik, Frankfurt, Federal Republic of Germany.
Pflugers Arch. 1987 Nov;410(4-5):487-94. doi: 10.1007/BF00586530.
Recent studies have demonstrated that active chloride secretion in mammalian colon and other epithelia, is dependent on the induction of an increase of apical chloride conductance. Since the physical characteristics of apical chloride channels in man have not been elucidated, patch clamp analysis of human colon cells (HT29), in culture, was performed, after stimulation with db-cAMP 10(-4) mol/l. In excised inside out patches of apical membranes two types of channels were found. The smaller and less frequent channel had a mean conductance of 15 +/- 1 pS (n = 9). This type of channel showed identical I/V curves in NaCl and KCl solutions. It was inhibited by a chloride channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB). The more frequently observed larger conductance channel was selective for anions and was impermeable to Na+ and K+. Regarding anion selectivity, the channel was similarly permeable to Cl-, Br-, I-, and NO3-, but was impermeable to gluconate. The channel was completely inhibited by the potent Cl- channel blocker NPPB (10(-6) mol/l). This channel exhibited rectification: The conductance was 50 +/- 4 pS at positive clamp potentials (sign referred to bath with respect to pipette interior) and 32 +/- 3 (n = 33) pS at negative voltages. Moreover, the open state probability was doubled when the clamp potential was increased from -20 to +20 mV. These results demonstrate the existence of chloride channels in the apical membrane of db-cAMP treated colonic carcinoma cells.
最近的研究表明，哺乳动物结肠及其他上皮组织中的主动氯离子分泌依赖于顶端氯离子电导的增加。由于人类顶端氯离子通道的物理特性尚未阐明，因此在用10(-4)mol/L的二丁酰环磷腺苷（db-cAMP）刺激后，对培养的人结肠细胞（HT29）进行了膜片钳分析。在切除的顶端膜内向外膜片中发现了两种类型的通道。较小且出现频率较低的通道平均电导为15±1 pS（n = 9）。这种类型的通道在NaCl和KCl溶液中显示出相同的电流-电压（I/V）曲线。它被氯离子通道阻滞剂5-硝基-2-(3-苯丙基氨基)-苯甲酸酯（NPPB）抑制。更常观察到的较大电导通道对阴离子具有选择性，对Na+和K+不可渗透。关于阴离子选择性，该通道对Cl-、Br-、I-和NO3-的通透性相似，但对葡萄糖酸盐不可渗透。该通道被强效Cl-通道阻滞剂NPPB（10(-6)mol/L）完全抑制。该通道表现出整流特性：在正向钳制电位下（相对于移液管内部，浴液为正）电导为50±4 pS，在负向电压下为32±3（n = 33）pS。此外，当钳制电位从-20 mV增加到+20 mV时，开放状态概率增加一倍。这些结果证明了经db-cAMP处理的结肠癌细胞顶端膜中存在氯离子通道。
