Lomax R B, Herrero C J, García-Palomero E, García A G, Montiel C
Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
Cell Calcium. 1998 Apr;23(4):229-39. doi: 10.1016/s0143-4160(98)90121-x.
We have studied capacitative Ca2+ entry into Xenopus oocytes by depleting intracellular Ca2+ stores with inositol 1,4,5-trisphosphate or thapsigargin. Capacitative Ca2+ entry was evoked by hyperpolarisation and monitored via the Ca(2+)-activated Cl- current. Hyperpolarisation-evoked currents increased with extracellular [Ca2+] in the range 0.9-5 mM, and were reversibly inhibited by extracellular Mg2+ (0.1-10 mM) by up to 60%. Currents were decreased by the voltage-gated Ca2+ channel antagonists omega-conotoxin GVIA, MVIIA and MVIIC (0.3-10 microM) and the inhibition of Ca2+ entry in individual oocytes by omega-conotoxins GVIA and MVIIA was highly heterogeneous, but not additive. Flunarizine (10 microM) and the imidazoles SK&F 96365 (10 microM), miconazole (40 microM) and econazole (40 microM) partly blocked Ca2+ entry. Ca2+ entry was unaffected by calciseptine (300 nM) or alpha-bungarotoxin (1 microM). The possibility that these compounds might inhibit the Ca(2+)-activated Cl- current rather than capacitative Ca2+ entry itself was examined by recording the Cl- current activated by the increase in [Ca2+]i activated by the flash photolysis of caged Ca2+. Eicosatetraynoic acid (2-10 microM) markedly inhibited, and La3+ (1 mM but not 100 microM) potentiated the increase in Ca(2+)-activated Cl- current. In contrast, omega-conotoxins and Mg2+ had no effect on the Ca(2+)-activated Cl- current itself. These findings support the hypothesis that capacitative Ca2+ entry into Xenopus oocytes occurs through channels with a pharmacology similar to that of neuronal non-L type voltage-gated Ca2+ channels.
我们通过用肌醇1,4,5 - 三磷酸或毒胡萝卜素耗尽细胞内钙库，研究了非洲爪蟾卵母细胞中的容量性钙内流。容量性钙内流由超极化诱发，并通过钙激活氯离子电流进行监测。超极化诱发的电流在细胞外[Ca2 +]浓度为0.9 - 5 mM范围内随其升高而增加，并被细胞外Mg2 +（0.1 - 10 mM）可逆性抑制达60%。电流被电压门控钙通道拮抗剂ω - 芋螺毒素GVIA、MVIIA和MVIIC（0.3 - 10 μM）降低，并且ω - 芋螺毒素GVIA和MVIIA对单个卵母细胞钙内流的抑制高度不均一，但无累加效应。氟桂利嗪（10 μM）以及咪唑类药物SK&F 96365（10 μM）、咪康唑（40 μM）和益康唑（40 μM）部分阻断钙内流。钙内流不受钙调蛋白（300 nM）或α - 银环蛇毒素（1 μM）影响。通过记录由笼锁钙的闪光光解激活的细胞内[Ca2 +]增加所激活的氯离子电流，研究了这些化合物可能是抑制钙激活氯离子电流而非容量性钙内流本身的可能性。二十碳四炔酸（2 - 10 μM）显著抑制，而La3 +（1 mM而非100 μM）增强钙激活氯离子电流的增加。相反，ω - 芋螺毒素和Mg2 +对钙激活氯离子电流本身无影响。这些发现支持这样的假说，即非洲爪蟾卵母细胞中的容量性钙内流是通过与神经元非L型电压门控钙通道药理学特性相似的通道发生的。
