Kaiho H, Kimura J, Matsuoka I, Kumasaka T, Nakanishi H
Department of Pharmacology, Fukushima Medical College, Fukushima, Japan.
J Neurochem. 1996 Jul;67(1):398-406. doi: 10.1046/j.1471-4159.1996.67010398.x.
ATP (1 mM) induced a biphasic increase in intracellular Ca2+ concentration ([Ca2+]i), i.e., an initial transient increase decayed to a level of sustained increase, in NG108-15 cells. The transient increase was inhibited by a phospholipase C inhibitor, 1-[6[[17beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H- pyrrole-2,5-dione (U73122), whereas the sustained increase was abolished by removal of external Ca2+. We examined the mechanism of the ATP-elicited sustained [Ca2+]i increase using the fura-2 fluorescent method and the whole-cell patch clamp technique. ATP (1 mM) induced a membrane current with the reversal potential of 12.5 +/- 0.8 mV (n = 10) in Tyrode external solution. The EC50 of ATP was approximately 0.75 mM. The permeability ratio of various cations carrying this current was Na+ (defined as 1) > Li+ (0.92 +/- 0.01; n = 5) > K+ (0.89 +/- 0.03; n = 6) > Rb+ (0.55 +/- 0.02; n = 6) > Cs+ (0.51 +/- 0.01; n = 5) > Ca2+ (0.22 +/- 0.03; n = 3) > N-methyl-D-glucamine (0.13 +/- 0.01; n = 5), suggesting that ATP activated a nonselective cation current. The ATP-induced current was larger at lower concentrations of external Mg2+. ATP analogues that induced the current were 2-methylthio-ATP (2MeSATP), benzoylbenzoic-ATP, adenosine 5'-thiotriphosphate (ATPgammaS), and adenosine 5'-O-(2-thiodiphosphate), but not adenosine, ADP, alpha,beta-methylene-ATP (AMPCPP), beta,gamma-methylene-ATP (AMPPCP), or UTP. Concomitant with the current data, 2MeSATP and ATPgammaS, but not AMPCPP or AMPPCP, increased the sustained [Ca2+]i increase. We conclude that ATP activates a class of Ca2+-permeable nonselective cation channels via the P2z receptor in NG108-15 cells.
在NG108 - 15细胞中，1 mM的ATP可诱导细胞内钙离子浓度（[Ca2+]i）呈双相增加，即最初的短暂增加随后衰减至持续增加的水平。磷脂酶C抑制剂1 - [6[[17β - 3 - 甲氧基雌甾 - 1,3,5(10) - 三烯 - 17 - 基]氨基]己基] - 1H - 吡咯 - 2,5 - 二酮（U73122）可抑制这种短暂增加，而去除细胞外Ca2+则可消除持续增加。我们使用fura - 2荧光法和全细胞膜片钳技术研究了ATP引发的[Ca2+]i持续增加的机制。在Tyrode细胞外溶液中，1 mM的ATP诱导出一种反转电位为12.5±0.8 mV（n = 10）的膜电流。ATP的半数有效浓度（EC50）约为0.75 mM。携带这种电流的各种阳离子的通透率为Na+（定义为1）> Li+（0.92±0.01；n = 5）> K+（0.89±0.03；n = ⑥）> Rb+（0.55±0.02；n = ⑥）> Cs+（0.51±0.01；n = ⑤）> Ca2+（0.22±0.03；n = ③）> N - 甲基 - D - 葡糖胺（0.13±0.01；n = ⑤）,这表明ATP激活了一种非选择性阳离子电流。在较低浓度的细胞外Mg2+条件下，ATP诱导的电流更大。能够诱导这种电流的ATP类似物有2 - 甲硫基 - ATP（2MeSATP）、苯甲酰苯甲酸 - ATP、腺苷5'-硫代三磷酸（ATPγS）和腺苷5'-O-(2 - 硫代二磷酸)，但腺苷、ADP、α,β - 亚甲基 - ATP（AMPCPP）、β,γ - 亚甲基 - ATP（AMPPCP）或UTP则不能。与电流数据一致，2MeSATP和ATPγS能增加[Ca2+]i的持续增加，而AMPCPP或AMPPCP则不能。我们得出结论，在NG108 - 15细胞中，ATP通过P2z受体激活了一类Ca2+通透的非选择性阳离子通道。
