Tamagawa T, Henquin J C
Diabetes. 1983 May;32(5):416-23. doi: 10.2337/diab.32.5.416.
Substitution of extracellular Cl- by impermeant isethionate (5 mM residual Cl-) caused a monophasic inhibition of glucose-stimulated insulin release, accompanied by an initial transient increase and a secondary lasting decrease in 86Rb+ efflux from perifused islets. Cl- reintroduction restored insulin release with an overshoot above control values and successively produced a small decrease and a large increase in efflux. Theophylline potentiated the insulinotropic effect of glucose more markedly at low Cl- than at normal Cl-, but did not restore a normal rate of 86Rb+ efflux. Lowering the concentration of Cl- did not alter the effect of glucose, tolbutamide, or arginine on 86Rb+ efflux, but simply shifted the efflux rates to lower values. The first phase of glucose-stimulated insulin release was not modified, but the second phase was inhibited. The insulinotropic effect of tolbutamide was augmented at low Cl- and that of arginine (at 7 mM glucose) was not affected. In incubated islets, the stimulation of insulin release by glyceraldehyde was barely inhibited when Cl- was substituted by isethionate and the marked decrease of the effect of glucose could be prevented by glutamine. In a glucose-free, low Cl- medium, the insulinotropic effect of leucine, arginine, and lysine was inhibited; this inhibition was reversed by glutamine, but not by theophylline. Lowering the concentration of Cl- had no effect on 45Ca2+ influx or efflux in the absence of glucose, did not alter the increase in influx and efflux during the first 5 min of glucose stimulation, but impaired both influx and efflux during the second phase. Leucine-induced 45Ca2+ uptake was inhibited at low Cl- and this inhibition was prevented by glutamine. In conclusion, islet cells possess a Cl- -activated modality of K efflux, which does not seem to play a role in the stimulus-secretion coupling. Since Cl- substitution by an impermeant anion does not inhibit the stimulation of insulin release by all agents, the role of Cl- ions does not appear to be restricted to a chemiosmotic mechanism of exocytosis. No single mechanism explains the multiple changes in B-cell function resulting from the decrease in Cl- concentration, but it is proposed that some of them could result from modifications of intracellular pH.
用不可渗透的羟乙基磺酸（残余氯离子浓度为5 mM）替代细胞外氯离子，导致葡萄糖刺激的胰岛素释放呈单相抑制，同时，来自灌流胰岛的86Rb+外流先出现短暂增加，随后持续减少。重新引入氯离子可恢复胰岛素释放，且释放量超过对照值，并相继使外流先小幅减少，后大幅增加。在低氯离子浓度下，茶碱比在正常氯离子浓度下更显著地增强了葡萄糖的促胰岛素分泌作用，但未恢复86Rb+外流的正常速率。降低氯离子浓度并未改变葡萄糖、甲苯磺丁脲或精氨酸对86Rb+外流的作用，只是将外流速率移至较低值。葡萄糖刺激的胰岛素释放的第一相未改变，但第二相受到抑制。在低氯离子浓度下，甲苯磺丁脲的促胰岛素分泌作用增强，而精氨酸（在7 mM葡萄糖浓度下）的作用不受影响。在孵育的胰岛中，当用羟乙基磺酸替代氯离子时，甘油醛对胰岛素释放的刺激作用几乎未受抑制，且谷氨酰胺可防止葡萄糖作用的显著降低。在无葡萄糖的低氯离子培养基中，亮氨酸、精氨酸和赖氨酸的促胰岛素分泌作用受到抑制；这种抑制作用可被谷氨酰胺逆转，但不能被茶碱逆转。在无葡萄糖时，降低氯离子浓度对45Ca2+内流或外流无影响，在葡萄糖刺激的最初5分钟内不改变内流和外流的增加，但在第二阶段损害了内流和外流。在低氯离子浓度下，亮氨酸诱导的45Ca2+摄取受到抑制，且谷氨酰胺可防止这种抑制。总之，胰岛细胞具有一种氯离子激活的钾外流模式，这似乎在刺激-分泌偶联中不起作用。由于用不可渗透的阴离子替代氯离子并不抑制所有物质对胰岛素释放的刺激，氯离子的作用似乎不限于胞吐作用的化学渗透机制。没有单一机制能解释因氯离子浓度降低导致的B细胞功能的多种变化，但有人提出其中一些变化可能是由细胞内pH的改变引起的。
