Kamouchi M, Droogmans G, Nilius B
Laboratorium voor Fysiologie, KU Leuven, Belgium.
Gen Physiol Biophys. 1999 Jun;18(2):199-208.
We have used combined patch clamp and fura-2 fluorescence to elucidate the role of membrane potential in the regulation of the cytosolic Ca2+ concentration ([Ca2+]i) in a human umbilical vein derived endothelial cell-line, EA.hy926 (EA cells) stimulated with vasoactive agonists, such as ATP, histamine and bradykinin. This stimulation caused hyperpolarization and sustained Ca2+ plateau in nonclamped cells. Clamping agonist-stimulated cells at negative potentials enhanced the amplitude of this plateau, whereas it was smaller at more depolarized potentials, indicating that Ca2+ influx follows its driving force. Depolarization of the membrane by increasing extracellular K+ or by applying charybdotoxin, a blocker of big conductance Ca2+-dependent K+ channels during agonist stimulation diminished the plateau rise in [Ca2+]i. It is concluded that the membrane potential is an efficient regulator of Ca2+ influx during the plateau phase of agonist-mediated Ca2+ signals. In addition, the modulating effects on Ca2+ signals should be interpreted with caution if the membrane potential of the cells is not controlled.
我们运用膜片钳和fura-2荧光技术相结合的方法，来阐明膜电位在调节人脐静脉来源的内皮细胞系EA.hy926（EA细胞）胞质Ca2+浓度（[Ca2+]i）中的作用，该细胞系受到血管活性激动剂如ATP、组胺和缓激肽的刺激。这种刺激在未钳制的细胞中引起超极化和持续的Ca2+平台期。在负电位下钳制激动剂刺激的细胞会增强该平台期的幅度，而在更正的去极化电位下则较小，这表明Ca2+内流遵循其驱动力。在激动剂刺激期间，通过增加细胞外K+或应用大电导Ca2+依赖性K+通道阻滞剂辣椒毒素使细胞膜去极化，会减少[Ca2+]i的平台期升高。得出的结论是，膜电位是激动剂介导的Ca2+信号平台期Ca2+内流的有效调节因子。此外，如果细胞的膜电位未得到控制，对Ca2+信号的调节作用应谨慎解释。
