N-methyl-D-aspartate excitotoxicity:: Relationships among plasma membrane potential, Na+/Ca2+ exchange, mitochondrial Ca2+ overload, and cytoplasmic concentrations of Ca2+, H+, and K+
N-methyl-D-aspartate excitotoxicity:: Relationships among plasma membrane potential, Na+/Ca2+ exchange, mitochondrial Ca2+ overload, and cytoplasmic concentrations of Ca2+, H+, and K+
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DOI：
10.1124/mol.56.3.619
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发表时间：
1999-09-01
影响因子：
3.6
通讯作者：
Kiedrowski, L
中科院分区：
文献类型：
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作者：
Kiedrowski, L
高Na+浓度下N-甲基-D-天冬氨酸(NMDA)诱导的兴奋性毒性可能通过Na+/Ca~(2+)交换器(NaCaX)的反向操作促进Ca~(2+)内流，但可能同时通过去极化质膜(PM)而降低电化学Ca~(2+)驱动力；利用数字荧光显微镜比较Na~+与不支持NaCaX操作的离子，即N-甲基-D-氨基葡萄糖胺(+)或Li+对PM电位的影响；细胞内Ca~(2+)、H~+和K+浓度；线粒体Ca~(2+)储存；以及暴露于NMDA受体激动剂的原代培养谷物颗粒细胞的存活。在Na+或Li+存在时，NMDA使质膜去极化，降低胞浆pH(pH(C))；在Li+存在时，细胞内钙内流减少，线粒体未发生钙超载，细胞质比Na+更酸化。在N-甲基-D-葡萄糖胺(+)存在下，NMDA使质膜立即超极化，但PM电位和pH(C)的进一步变化是钙依赖的。在无钙时，超极化持续，pH(C)下降非常缓慢，K+保留在细胞质中，小脑颗粒细胞存活；有钙时，pH(C)迅速下降，跨PM的K+浓度梯度开始崩溃，钙离子内流和兴奋毒性大大增加。这些结果表明，NMDA诱导的钙内流的主要成分，很可能是兴奋毒性成分，是由反向NaCaX介导的，而通过NMDA通道的直接钙内流被钠依赖的PM去极化所抑制。
A high cytoplasmic Na+ concentration may contribute to N-methyl-D-aspartate (NMDA)-induced excitotoxicity by promoting Ca2+ influx via reverse operation of the Na+/Ca2+ exchanger(NaCaX), but may simultaneously decrease the electrochemical Ca2+ driving force by depolarizing the plasma membrane (PM); Digital fluorescence microscopy was used to compare the effects of Na+ versus ions that do not support the NaCaX operation, i.e., N-methyl-D-glucamine(+) or Li+, on: PM potential; cytoplasmic concentrations of Ca2+, H+, and K+; mitochondrial Ca2+ storage; and viability of primary cultures of cerebellar granule cells exposed to NMDA receptor agonists. In the presence of Na+ or Li+, NMDA depolarized the PM and decreased cytoplasmic pH (pH(C)); in the presence of Li+, Ca2+ influx was reduced, mitochondrial Ca2+ overload did not occur, and the cytoplasm became more acidified than in the presence of Na+. In the presence of N-methyl-D-glucamine(+), NMDA instantly hyperpolarized the PM, but further changes in PM potential and pH(C) were Ca-dependent. In the absence of Ca2+, hyperpolarization persisted, pH(C) was decreasing very slowly, K+ was retained in the cytoplasm, and cerebellar granule cells survived the challenge; in the presence of Ca2+, pH(C) dropped rapidly, the K+ concentration gradient across the PM began to collapse as the PM began to depolarize, and Ca2+ influx and excitotoxicity greatly increased. These results indicate that the dominant, very likely excitotoxic, component of NMDA-induced Ca2+ influx is mediated by reverse NaCaX and that direct Ca2+ influx via NMDA channels is curtailed by Na-dependent PM depolarization.