Soria B, Chanson M, Giordano E, Bosco D, Meda P
Department of Physiology, School of Medicine, University of Alicante, Spain.
Diabetes. 1991 Aug;40(8):1069-78. doi: 10.2337/diab.40.8.1069.
To assess whether different electrophysiological characteristics could account for the heterogeneous secretion of individual beta-cells in vitro, we used patch-clamp configurations to study currents in plaque-forming (insulin-secreting) and non-plaque-forming rat pancreatic beta-cells that were distinguished in a reverse hemolytic plaque assay (RHPA) after a 30-min stimulation by 16.7 mM glucose. RHPA showed that the population of single beta-cells under study was stimulated (P less than 0.01-0.001) to secrete insulin by 16.7 mM glucose, 100 microM tolbutamide, 20 microM glyburide, or 30 mM KCl but, under these conditions, also comprised beta-cells that did not secrete detectable amounts of insulin. Under current clamp conditions, secreting and nonsecreting beta-cells showed analogous resting membrane potentials (approximately 60 mV) and were similarly depolarized by 30 mm KCl and 100 microM tolbutamide. Under voltage-clamp conditions, total membrane conductance (approximately 6 nS) was also similar in the glucose-responsive and -unresponsive beta-cells, which, when monitored in the whole-cell configuration after RHPA, showed the following currents: a voltage-dependent Na+ current, a voltage-activated Ba2+ current, a voltage-dependent K+ delayed-rectifier current, a voltage-dependent Ca(2+)-activated K+ current, and a voltage-independent and tolbutamide-sensitive K+ current. In the cell-attached configuration and the presence of 2.8 mM glucose, secreting and nonsecreting beta-cells displayed a similar single-channel activity that was abolished when glucose concentration was raised to 16.7 mM. We conclude that beta-cells studied after RHPA have an electrically normal membrane whether they release insulin in response to 16.7 mM glucose or not.
为了评估不同的电生理特性是否可以解释体外单个β细胞的异质性分泌，我们采用膜片钳技术研究了在16.7 mM葡萄糖刺激30分钟后，在反向溶血空斑试验（RHPA）中区分出的形成斑块（分泌胰岛素）和不形成斑块的大鼠胰腺β细胞中的电流。RHPA显示，所研究的单个β细胞群体受到16.7 mM葡萄糖、100 μM甲苯磺丁脲、20 μM格列本脲或30 mM氯化钾刺激后分泌胰岛素（P小于0.01 - 0.001），但在这些条件下，也包含不分泌可检测量胰岛素的β细胞。在电流钳制条件下，分泌和不分泌胰岛素的β细胞显示出类似的静息膜电位（约60 mV），并且被30 mM氯化钾和100 μM甲苯磺丁脲类似地去极化。在电压钳制条件下，葡萄糖反应性和无反应性β细胞的总膜电导（约6 nS）也相似，在RHPA后以全细胞模式监测时，它们显示出以下电流：电压依赖性Na +电流、电压激活的Ba2 +电流、电压依赖性K +延迟整流电流、电压依赖性Ca(2 +)激活的K +电流以及电压非依赖性和甲苯磺丁脲敏感性K +电流。在细胞贴附模式和2.8 mM葡萄糖存在的情况下，分泌和不分泌胰岛素的β细胞表现出类似的单通道活性，当葡萄糖浓度升至16.7 mM时该活性被消除。我们得出结论，在RHPA后研究的β细胞，无论它们是否对16.7 mM葡萄糖释放胰岛素，其膜在电方面都是正常的。
