Oscillations of membrane potential and cytosolic Ca2+ concentration in SUR1-/- beta cells
Oscillations of membrane potential and cytosolic Ca2+ concentration in SUR1-/- beta cells
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DOI：
10.1007/s00125-004-1348-0
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发表时间：
2004-03-01
期刊：
影响因子：
8.2
通讯作者：
Drews, G
中科院分区：
文献类型：
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作者：
Düfer, M;Haspel, D;Drews, G
目标/假设。缺乏功能性K-ATP通道的SUR1(ABCC8)(-/-)小鼠是检测K-ATP通道在β细胞功能中意义的合适模型。我们研究了这种基因缺失是如何干扰刺激-分泌耦合的。我们测试了代谢抑制和甘丙素的影响，其作用方式存在争议。用微电极或膜片钳技术测定细胞质膜电位(Vm)和电流，用荧光染料测定细胞内钙离子浓度([Ca~(2+)](C))和线粒体膜电位(DeltaPsi)。与对照组相比，SUR1(-/-)β细胞即使在低糖浓度下也表现出电活动。用膜片钳技术可检测到持续的尖峰活动，但在微电极上可检测到由钙依赖的动作电位爆发组成的慢振荡。[Ca~(2+)](C)表现出各种振荡或持续增加的模式。叠氮钠不能使SUR1(-/-)β细胞超极化。叠氮钠对SUR1(-/-)细胞的DeltaPsi去极化作用明显低于SUR1(+/+)细胞。甘丙肽瞬时降低SUR1(-/-)和SUR1(+/+)小鼠细胞动作电位频率和[Ca~(2+)](C)。在SUR1(+/+)β细胞中观察到的Vm和[Ca~(2+)](C)对葡萄糖浓度的强烈依赖性在基因敲除细胞中被破坏。这表明，这两个参数在没有功能K-ATP通道的情况下都是振荡的。叠氮钠缺乏代谢抑制作用，表明在SUR1(-/-)β细胞中，ATP/ADP的变化不再将葡萄糖代谢与VM联系起来。甘丙肽的研究结果表明，这种多肽独立于K-ATP电流影响β细胞，因此可能有助于调节SUR1(-/-)动物的β细胞功能。
Aims/hypothesis. SUR1(ABCC8)(-/-) mice lacking functional K-ATP channels are an appropriate model to test the significance of K-ATP channels in beta-cell function. We examined how this gene deletion interferes with stimulus-secretion coupling. We tested the influence of metabolic inhibition and galanin, whose mode of action is controversial.Methods. Plasma membrane potential (Vm) and currents were measured with microelectrodes or the patch-clamp technique; cytosolic Ca2+ concentrations ([Ca2+](c)) and mitochondrial membrane potential (DeltaPsi) were measured using fluorescent dyes.Results. In contrast to the controls, SUR1(-/-) beta cells showed electrical activity even at a low glucose concentration. Continuous spike activity was measured with the patch-clamp technique, but with microelectrodes slow oscillations in Vm consisting of bursts of Ca2+-dependent action potentials were detected. [Ca2+](c) showed various patterns of oscillations or a sustained increase. Sodium azide did not hyperpolarize SUR1(-/-) beta cells. The depolarization of DeltaPsi evoked by sodium azide was significantly lower in SUR1(-/-) than SUR1(+/+) cells. Galanin transiently decreased action potential frequency and [Ca2+](c) in cells from both SUR1(-/-) and SUR1(+/+) mice.Conclusion/interpretation. The strong dependence of Vm and [Ca2+](c) on glucose concentration observed in SUR1(+/+) beta cells is disrupted in the knock-out cells. This demonstrates that both parameters oscillate in the absence of functional K-ATP channels. The lack of effect of metabolic inhibition by sodium azide shows that in SUR1(-/-) beta cells changes in ATP/ADP no longer link glucose metabolism and Vm. The results with galanin suggest that this peptide affects beta cells independently of K-ATP currents and thus could contribute to the regulation of beta-cell function in SUR1(-/-) animals.