不同浓度葡萄糖对大鼠胰岛β细胞L-型钙通道的影响

EFFECT OF DIFFERENT CONCENTRATION GLUCOSE ON THE VOLTAGE-DEPENDENT L-TYPE CALCIUM CHANNELS OF RAT PANCREATIC BETA CELLS

采用全细胞膜片钳技术观察不同浓度葡萄糖对新生Wister大鼠胰岛β细胞膜上电压依赖性L-型钙离子通道门控特性的影响,即分别用2.8、5.5、16.7和22.2mmol/L的葡萄糖刺激单个贴壁胰岛β细胞,以Ba2+作为载流子,分析比较葡萄糖对L-型钙通道电流的影响。结果显示:在低糖(2.8mmol/L)情况下,大鼠胰岛β细胞电压依赖性L-型钙离子通道电流静息膜电位约为-70mV,钙离子内流不明显,且无明显的时间依赖性关系。在葡萄糖浓度为5.5mmol/L的条件下,大鼠胰岛β细胞电压依赖性L-型钙离子通道电流在-40mV激活,+20mV左右达峰值;高糖(16.7mmol/L)作用胰岛β细胞后,电压依赖性L-型钙离子通道电流约-40mV激活,+10mV左右达峰值,即峰值电位向负方向移动约10mV;葡萄糖浓度达22.2mmol/L时,电活动呈持续性去极化,峰值电位增加不明显,提示葡萄糖降低胰岛β细胞电压依赖性L-型钙通道电流的激活电位阈值,促进其开放,钙电流峰值电位增加,随着高糖作用时间的延长,胰岛β细胞容积变大,细胞膜破坏。提示高浓度葡萄糖在一定范围内可以刺激胰岛素的分泌,但浓度过高则可抑制胰岛素的分泌,通过观察葡萄糖刺激的胰岛β细胞胰岛素第一时相分泌的变化,在一定程度上对高糖毒性作用的可能提供了证据。

To observe the effects of different concentration glucose on the gating characteristics of the voltage-dependent L-type calcium ion channels of rat pancreatic beta cells cultured in vitro, the single pancreatic beta cell was stimulated with 2.8, 5.5, 16.7, 22.2 mmol/L glucose separately, by whole-cell patch technique, using Ba^2＋ as current cartier, the voltage-dependent L-type calcium channels current were recorded on plasma membrane, the effects of glucose on calcium channels current and cytoplasm free Ca^2＋ concentration were analysed. Results showed： After low concentration glucose （2.8 mmol/L） acted on the single pancreatic beta cell, the voltage-dependent L-type calcium channels current was not recorded, static state membrane potential is -70 mV, and there was no visible relation in time-dependent. At 5.5 mmol/L glucose concentration, the voltage-dependent L-type calcium channels current on plasma membrane of the single pancreatic beta cell was recorded. The voltage-dependent L-type calcium channels were the main Ca^2＋ channels on rat pancreatic beta cells membrane. It was activated at -40 mV, the peak amplitude of calcium current was at 20 mV. After high concentration glucose （16.7 mmol/L） acted on the pancreatic β cell, It was activated at -40 mV, the peak amplitude of the voltage-dependent L-type calcium channels current was at 10 mV, the peak current potential shifted 10 mV to negative direction. At 22.2 mmol/L glucose concentration, electrical bursting was lasting depolarization, there was no obvious increasing in calcium current peak amplitude. It was suggested： high concentration glucose lowered the active potential threshold of the voltage-dependent L-type calcium channels current, increased calcium current peak amplitude, high concentration glucose could promote the voltage-dependent L-type calcium channels to open for a brief period, as the action time extended, the volume of the single pancreatic beta cells became big and the cells were broken, It suggested high concentration glucose could promote insulin to secret at certain concentration range, or it could inhibit insulin release from pancreatic islets. By observing the change of the first phase of glucose-stimulated insulin secretion from the rat pancreatic islets, it could provide evidence to some extent for poisonous action of high concentration glucose to the pancreatic beta cells.