PLATEAU POTENTIALS IN PANCREATIC-ISLET CELLS ARE VOLTAGE-DEPENDENT ACTION-POTENTIALS
PLATEAU POTENTIALS IN PANCREATIC-ISLET CELLS ARE VOLTAGE-DEPENDENT ACTION-POTENTIALS
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DOI：
10.1038/286404a0
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发表时间：
1980-01-01
期刊：
影响因子：
64.8
通讯作者：
PORTE, D
中科院分区：
文献类型：
--
作者：
COOK, DL;CRILL, WE;PORTE, D
在一定阈值（通常为5-7 mM）以上的稳定葡萄糖浓度刺激下，胰岛细胞显示出周期性膜电位变化1。这种胰岛电活动由叠加在去极化平台上的动作电位（尖峰）组成（见图1）。较高水平的葡萄糖延长了平台期并缩短了沉默期，直到平台电位合并以在20-25 mM产生连续尖峰。在平台期中花费的每个周期的分数与葡萄糖浓度和胰岛素释放速率2相关，这表明控制平台期的开始和偏移在胰岛素释放的调节中是重要的。静止期和平台期之间的突然转换表明，平台期是一种持续的、电压依赖性的动作电位，就像在心肌中一样。这一观点得到了证据3的支持，即胰岛的K+去极化刺激了Ca 2+内流。然而，这种电压依赖性可以通过电证据4，5解释，尖峰是由电压依赖性钙电流产生的。此外，有证据反对平台的电压依赖性，因为它似乎不受细胞内电流注入和K+去极化的影响，这明显影响了尖峰5，6。由于对这些最后的阴性结果有其他解释（见下文），我们使用一种新技术重新研究了这一重要问题，该技术使用抽吸电极直接电刺激整个孤立的胰岛。与以前的否定结果相反，我们现在的结果清楚地表明，平台电位是一个电压依赖性的，持续的动作电位。
Islet cells stimulated by a steady glucose concentration above a certain threshold (usually 5–7 mM) display cyclic membrane potential changes1. This islet electrical activity consists of action potentials (spikes) superimposed on a depolarized plateau (see Fig. 1). Higher levels of glucose prolong the plateau phase and shorten the silent phase until the plateau potentials merge to produce continuous spiking at 20–25 mM. The fraction of each cycle spent in the plateau phase correlates with glucose concentration and insulin release rate2, suggesting that control of the onset and offset of the plateau is important in the regulation of insulin release. The abrupt transitions between silent and plateau phases suggest that the plateau is a persistent, voltage-dependent action potential as in cardiac muscle. This idea is supported by evidence3that Ca2+influx is stimulated by K+depolarization of islets. However, this voltage dependency can be explained by electrical evidence4,5that the spikes are generated by voltage-dependent Ca2+currents. Furthermore, there is evidence against the voltage dependency of the plateau because it seemed to be unaffected by intracellular current injection and K+depolarization, which clearly affected spiking5,6. As there are alternative explanations (see below) for these last negative findings, we have re-examined this important question using a new technique of direct electrical stimulation of entire, isolated islets using a suction electrode. Contrary to the previous negative findings, our present results clearly show that the plateau potential is a voltage-dependent, persistent action potential.