Temporal patterns of changes in ATP/ADP ratio, glucose 6-phosphate and cytoplasmic free Ca2+ in glucose-stimulated pancreatic beta-cells
Temporal patterns of changes in ATP/ADP ratio, glucose 6-phosphate and cytoplasmic free Ca2+ in glucose-stimulated pancreatic beta-cells
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DOI：
10.1042/bj3140091
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发表时间：
1996-02-15
影响因子：
4.1
通讯作者：
Tornheim, K
中科院分区：
文献类型：
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作者：
Nilsson, T;Schultz, V;Tornheim, K
ATP 敏感的 K+ (K-ATP) 通道的关闭是胰腺 β 细胞中刺激-分泌耦合机制的一部分，导致膜去极化和 Ca2+ 通过电压敏感的 L 型 Ca2+ 通道流入。在高水平葡萄糖存在下观察到的 ATP/ADP 比率升高被认为介导了葡萄糖诱导的 K-ATP 通道关闭和细胞质游离 Ca2+ 浓度 ([Ca2+](i)) 的升高，或者是 [Ca2+](i) 增加激活线粒体脱氢酶的结果。为了区分这两种可能性，将 ATP/ADP 比率变化的时间过程与 [Ca2+](i) 的变化进行比较来确定。我们在此表明，用葡萄糖刺激小鼠胰腺 β 细胞悬浮液后，ATP/ADP 比率迅速增加数倍。 ATP/ADP 比率的变化是一个早期事件，在 20-40 秒内开始，并且先于 [Ca2+](i) 上升。时间关系表明腺嘌呤核苷酸的变化不可能是[Ca2+](i)变化的结果，而可能确实是葡萄糖代谢和[Ca2+](i)变化之间的联系。当细胞依次用高浓度葡萄糖、可乐定和最后高浓度细胞外Ca2+处理以诱导细胞悬液中[Ca2+](i)的同步振荡时，观察到ATP/ADP比率的相应振荡。 6-磷酸葡萄糖水平与 ATP/ADP 比率异相振荡。这些结果支持这样的假设：先前在葡萄糖刺激的单个胰岛或β细胞中观察到的Ca2+振荡可能反映了伴随振荡糖酵解的ATP/ADP比率的振荡。
Closure of ATP-sensitive K+ (K-ATP) channels is part of the stimulus-secretion coupling mechanism in the pancreatic beta-cell, leading to membrane depolarization and influx of Ca2+ through voltage-sensitive L-type Ca2+ channels. The elevated ATP/ADP ratio seen in the presence of high levels of glucose has been postulated to mediate the glucose-induced closure of the K-ATP channels and rise in cytoplasmic free Ca2+ concentration ([Ca2+](i)), or alternatively to be a consequence of activation of mitochondrial dehydrogenases by the increase in [Ca2+](i). To distinguish between these two possibilities, the time course of the change in the ATP/ADP ratio was determined in comparison with that of [Ca2+](i). We here show that a severalfold rise in the ATP/ADP ratio occurs rapidly on stimulation of suspensions of mouse pancreatic beta-cells with glucose. The change in the ATP/ADP ratio is an early event that begins within 20-40 s and precedes the rise in [Ca2+](i). The temporal relationship indicates that the adenine nucleotide changes cannot be a consequence of the [Ca2+](i) changes and may indeed be the connecting link between glucose metabolism and [Ca2+](i) changes. When the cells were sequentially treated with high glucose concentration, clonidine and finally high extracellular Ca2+ concentration to induce synchronized oscillations in [Ca2+](i) in the cell suspension, corresponding oscillations in the ATP/ADP ratio were observed. Glucose 6-phosphate levels oscillated out of phase with the ATP/ADP ratio. These results support the hypothesis that the Ca2+ oscillations previously observed in glucose-stimulated single islets or beta-cells may reflect oscillations in the ATP/ADP ratio that accompany oscillatory glycolysis.