Tsumura T, Oiki S, Ueda S, Okuma M, Okada Y
Department of Cellular and Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Japan.
Am J Physiol. 1996 Dec;271(6 Pt 1):C1872-8. doi: 10.1152/ajpcell.1996.271.6.C1872.
The sensitivity to extracellular nucleotides of volume-sensitive Cl- channel activity was investigated by whole cell and single-channel patch-clamp recordings in a human small intestinal epithelial cell line (Intestine 407) during steady osmotic swelling. Adenine nucleotides added to the bathing solution suppressed whole cell volume-sensitive Cl- currents with the potency sequence of ATP > ADP > AMP. In contrast, extracellular adenosine 3',5'-cyclic monophosphate (cAMP) at over 0.1 mM increased volume-sensitive Cl- currents in the entire voltage range examined, whereas guanosine 3',5'-cyclic monophosphate was without effect. Neither the single-channel conductance nor the open probability was affected by extracellular cAMP. Extracellular ATP (at over 30 microM), in the Mg(2+)-free form, inhibited the whole cell volume-sensitive Cl- current, preferentially in the outward direction. By exposure to extracellular ATP, the single Cl- channel current became flickery at positive potentials. These results indicate that the volume-sensitive Cl- channel in the human epithelial cell is stimulated voltage independently by extracellular cAMP but blocked voltage dependently by the Mg(2+)-free form of extracellular ATP.
在人小肠上皮细胞系（Intestine 407）的稳定渗透肿胀过程中，通过全细胞和单通道膜片钳记录，研究了容积敏感性氯离子通道活性对细胞外核苷酸的敏感性。添加到浴液中的腺嘌呤核苷酸抑制全细胞容积敏感性氯电流，其效力顺序为ATP > ADP > AMP。相反，浓度超过0.1 mM的细胞外3',5'-环磷酸腺苷（cAMP）在整个检测电压范围内增加了容积敏感性氯电流，而3',5'-环磷酸鸟苷则无作用。单通道电导和开放概率均不受细胞外cAMP的影响。无镁形式的细胞外ATP（浓度超过30 μM）抑制全细胞容积敏感性氯电流，优先抑制外向电流。通过暴露于细胞外ATP，单个氯离子通道电流在正电位时变得闪烁。这些结果表明，人上皮细胞中的容积敏感性氯离子通道受细胞外cAMP的电压非依赖性刺激，但受无镁形式的细胞外ATP的电压依赖性阻断。
