Erecińska M, Nelson D, Dagani F, Deas J, Silver I A
Department of Pharmacology, University of Pennsylvania, Philadelphia 19104-6084.
J Neurochem. 1993 Oct;61(4):1356-68. doi: 10.1111/j.1471-4159.1993.tb13629.x.
Effects of nigericin were investigated in rat brain synaptosomes, cultured neurons, and C6 glioma cells to characterize the relations among ATP synthesis, [Na+]i, [K+]i, and [Ca2+]i, and pH under conditions when [H+]i is substantially increased and transmembrane electrical potential is decreased. Intracellular acidification and loss of K+ were accompanied by enhanced oxygen consumption and lactate production and a decrease in cellular energy level. Changes in the last three parameters were attenuated by addition of 1 mM ouabain. In synaptosomes treated with nigericin, neither respiration nor glycolysis was affected by 0.3 microM tetrodotoxin, whereas 1 mM amiloride reduced lactate production by 20% but did not influence respiration. In C6 cells, amiloride decreased the nigericin-stimulated rate of lactate generation by about 50%. The enhancement by nigericin of synaptosomal oxygen uptake and glycolytic rate decreased with time. However, there was only a small reduction in respiration and none in glycolysis in C6 cells. Measurements with ion-selective microelectrodes in neurons and C6 cells showed that nigericin also caused a rise in [Ca2+]i and [Na+]i. The increase in [Na+]i in C6 cells was partially reversed by 1 mM amiloride. It is concluded that nigericin-induced loss of K+ and subsequent depolarization lead to an increase in Na+ influx and stimulation of the Na+/K+ pump with a consequent rise in energy utilization; that acidosis inhibits mitochondrial ATP production; that a rise in [H+] does not decrease glycolytic rate when the energy state (a fall in [ATP] and rises in [ADP] and [AMP]) is simultaneously reduced; that a fall in [K+]i depresses both oxidative phosphorylation and glycolysis; and that the nigericin-induced alterations in ion levels and activities of energy-producing pathways can explain some of the deleterious effects of ischemia and hypoxia.
在大鼠脑突触体、培养的神经元和C6胶质瘤细胞中研究了尼日利亚菌素的作用，以表征在细胞内氢离子浓度大幅增加且跨膜电位降低的条件下，ATP合成、细胞内钠离子浓度、钾离子浓度和钙离子浓度以及pH值之间的关系。细胞内酸化和钾离子流失伴随着耗氧量增加、乳酸生成增加以及细胞能量水平降低。添加1 mM哇巴因可减弱后三个参数的变化。在用尼日利亚菌素处理的突触体中，0.3 μM河豚毒素对呼吸作用和糖酵解均无影响，而1 mM阿米洛利可使乳酸生成减少20%，但不影响呼吸作用。在C6细胞中，阿米洛利可使尼日利亚菌素刺激的乳酸生成速率降低约50%。尼日利亚菌素对突触体氧摄取和糖酵解速率的增强作用随时间而降低。然而，C6细胞中的呼吸作用仅略有降低，糖酵解则无变化。用离子选择性微电极对神经元和C6细胞进行测量表明，尼日利亚菌素还会导致细胞内钙离子浓度和钠离子浓度升高。C6细胞中细胞内钠离子浓度的升高可被1 mM阿米洛利部分逆转。研究得出的结论是，尼日利亚菌素诱导的钾离子流失及随后的去极化导致钠离子内流增加并刺激钠钾泵，从而使能量利用增加；酸中毒抑制线粒体ATP生成；当能量状态（ATP浓度降低、ADP和AMP浓度升高）同时降低时，氢离子浓度升高不会降低糖酵解速率；细胞内钾离子浓度降低会抑制氧化磷酸化和糖酵解；并且尼日利亚菌素诱导的离子水平变化和能量产生途径的活性变化可以解释缺血和缺氧的一些有害影响。
