Hanai H, Kameyama M, Kaneko E, Fujita M
National Institute for Physiological Sciences, Okazaki, Japan.
Pflugers Arch. 1991 Sep;419(2):184-9. doi: 10.1007/BF00373005.
Calcium transport systems of isolated ileal epithelial cells were investigated. The concentration of cytosolic free calcium ions, [Ca2+]i, was monitored with a fluorescent Ca2+ dye, fura-2. The fluorescence intensity ratio (I340/I380) was used as an index of [Ca2+]i. [Ca2+]i of the cells suspended in the nominally Ca(2+)-free solution was estimated at 52 +/- 3 nM. Ca2+ uptake was followed for as long as 5 min in the presence of 100-1000 microM added CaCl2. Most of the experiments were performed at 200 microM CaCl2. The Ca2+ uptake was abolished by 0.8 mM Ni2+ and 50 microM Mn2+ and partitally antagonized by 50 microM verapamil and 50 microM diltiazem but not affected by 20 microM nifedipine. The Ca2+ entry was reduced by increasing concentrations of extracellular K+ in the presence of valinomycin, suggesting a voltage-dependent nature of the uptake. On the other hand, the Ca2+ transport doubled in the presence of Bay K8644 (8 microM), a Ca2+ channel agonist. The Bay-K-8644-induced uptake was inhibited by either 10 microM nifedipine, 10 microM verapamil or 10 microM diltiazem and was relatively independent of extracellular K+ concentration. These results suggest that there are at least two distinct Ca2+ transport systems in the rat ileal epithelial cells, one resistant to organic Ca2+ channel blockers but relatively sensitive to membrane potential (basal uptake) and another inducible by Bay K 8644 and sensitive to the channel blockers but relatively independent of membrane potential.
对分离的回肠上皮细胞的钙转运系统进行了研究。用荧光钙染料fura-2监测胞质游离钙离子浓度[Ca2+]i。荧光强度比值（I340/I380）用作[Ca2+]i的指标。悬浮在名义上无钙溶液中的细胞的[Ca2+]i估计为52±3 nM。在添加100 - 1000 μM CaCl2的情况下，跟踪Ca2+摄取长达5分钟。大多数实验在200 μM CaCl2下进行。0.8 mM Ni2+和50 μM Mn2+可消除Ca2+摄取，50 μM维拉帕米和50 μM地尔硫卓可部分拮抗Ca2+摄取，但20 μM硝苯地平对其无影响。在缬氨霉素存在下，增加细胞外K+浓度可减少Ca2+内流，表明摄取具有电压依赖性。另一方面，在Ca2+通道激动剂Bay K8644（8 μM）存在下，Ca2+转运增加一倍。Bay-K-8644诱导的摄取受到10 μM硝苯地平、10 μM维拉帕米或10 μM地尔硫卓的抑制，并且相对独立于细胞外K+浓度。这些结果表明，大鼠回肠上皮细胞中至少存在两种不同的Ca2+转运系统，一种对有机Ca2+通道阻滞剂有抗性，但对膜电位相对敏感（基础摄取），另一种可被Bay K 8644诱导，对通道阻滞剂敏感，但相对独立于膜电位。
