Involvement of ATP-Sensitive K+ Channels in Free Radical–Mediated Inhibition of Insulin Secretion in Rat Pancreatic β-Cells
Involvement of ATP-Sensitive K+ Channels in Free Radical–Mediated Inhibition of Insulin Secretion in Rat Pancreatic β-Cells
复制标题
ATP 敏感性 K+ 通道参与自由基介导的大鼠胰腺 β 细胞胰岛素分泌抑制
DOI：
10.2337/diab.44.8.878
复制
发表时间：
1995
期刊：
影响因子：
7.7
通讯作者：
Hiromitsu Tanaka
中科院分区：
文献类型：
--
作者：
M. Nakazaki;M. Kakei;N. Koriyama;Hiromitsu Tanaka
为探讨氧自由基抑制胰岛β细胞胰岛素分泌的机制，采用膜片钳技术研究了H2 O2对胰岛β细胞膜电流的影响。β细胞暴露于H_2O_2（≥30 μmol/1）可增加ATP敏感性钾（K+ATP）通道的活性，但不改变细胞贴附膜的单通道电导。在11.1 mmol/l葡萄糖灌流过程中观察到的动作电流被抑制。在由内而外的膜片中，K+ATP通道的活性不受H_2O_2的影响。在常规的全细胞钳实验中，使用含有3 mmol/1 ATP的移液器溶液，H2 O2不影响膜电流。然而，过氧化氢激活K+ATP通道电流穿孔全细胞钳配置。随后暴露于11.1 mmol/12-酮异己酸可逆转增加的K+ATP通道电流。在细胞贴附膜片中，暴露于30 μmol/l H2 O2诱发的K+ATP通道电流被暴露于11.1 mmol/l甘油醛抑制，而暴露于0.3 mmol/l H2 O2再次激活通道。随后灌流11.1 mmol/L的2-酮异己酸抑制通道，这种效果被抵消暴露于10 mmol/L的H2 O2。在灌流2.8或11.1mmol/l葡萄糖时，用100 μmol/lH 2 O2洗脱后，可观察到K+ATP通道的瞬时抑制和动作电位的激发。我们得出结论，H2 O2对K+ATP通道没有直接影响，但当它暴露于β细胞时，在细胞代谢受到生理调节的条件下，它间接激活了通道。
To explore the mechanisms of inhibition of insulin secretion in pancreatic β-cells by oxygen free radicals, we studied the effects of H2O2 on membrane currents using the patch-clamp technique. Exposure of β-cells to H2O2 (≥30 (μmol/1) increased the activity of ATP-sensitive potassium (K+ATP) channels without changing the single channel conductance in cell-attached membrane patches. Action currents observed during superfusion of 11.1 mmol/1 glucose were suppressed. In inside-out membrane patches, the activity of K+ATP channels was not influenced by H2O2. In conventional whole-cell clamp experiments using a pipette solution containing 3 mmol/1 ATP, H2O2 did not influence the membrane currents. However, H2O2 did activate the K+ATP channel current in perforated whole-cell clamp configurations. The increased K+ATP channel current was reversed by subsequent exposure to 11.1 mmol/12-ketoisocaproic acid. In cell-attached membrane patches, the K+ATP channel current evoked by exposure to 30 μmol/l H2O2 was inhibited by exposure to 11.1 mmol/l glyceraldehyde, whereas the channel was again activated by exposure to 0.3 mmol/l H2O2. Subsequent superfusion of 11.1 mmol/l 2-ketoisocaproic acid inhibited the channel; this effect was counteracted by exposure to 10 mmol/l H2O2. Transient inhibition of K+ATP channels with provocation of action potentials was observed after washout of 100 μmol/l H2O2 during superfusion of 2.8 or 11.1 mmol/l glucose. We conclude that H2O2 has no direct effect on the K+ATP channels but that it indirectly activates the channels when it is exposed to β-cells under conditions in which the cellular metabolism is physiologically regulated.