Compound exocytosis in voltage-clamped mouse pancreatic β-cells revealed by carbon fibre amperometry
Compound exocytosis in voltage-clamped mouse pancreatic β-cells revealed by carbon fibre amperometry
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DOI：
10.1007/s004240050987
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发表时间：
2000-03-01
影响因子：
4.5
通讯作者：
Rorsman, P
中科院分区：
文献类型：
--
作者：
Bokvist, K;Holmqvist, M;Rorsman, P
胞吐的电容测量与碳纤维安培法相结合，用于对预加载胺- 5-羟色胺（5-HT）的单个胰岛素分泌小鼠胰腺β细胞的分泌特性进行时间分辨测量。葡萄糖诱导的电活动与反映血清素与胰岛素共同释放的短暂和瞬态安培电流的出现有关。由电压钳位去极化引起的综合安培响应与相应的电池电容增加成正比。这两个参数与膜电位呈u型关系，最大值在0 mV左右。在去极化开始和安培电流之间存在可变延迟（40-730 ms，平均230 ms）。在高频重复刺激期间，观察到胞吐能力逐渐下降（“抑制”）。这与安培反应的相应减少是平行的。利用碳纤维绘制β -中心的释放位点表明，胞吐作用局限于细胞中含有最高密度的分泌颗粒的部分。观察到两种类型的安培响应。在大约50%的细胞中，观察到平滑的增加，没有明显的离散事件。在剩下的细胞里。安培记录中有很大的尖峰。这些比单个分泌颗粒融合的预期大十倍或更多。我们认为三个大的尖峰反映了在胞吐之前在β细胞内形成的多颗粒复合物的胞吐。
Capacitance measurements of exocytosis were combined with carbon fibre amperometry for time-resolved measurements of the properties of secretion in single, insulin-secreting, mouse pancreatic beta-cells preloaded with the amine serotonin (5-HT). Glucose-induced electrical activity was associated with the appearance of brief and transient amperometric currents reflecting the serotonin co-released with insulin. The integrated amperometric responses resulting from voltage-clamp depolarisations were proportional to the corresponding increase in cell capacitance. Both parameters exhibited U-shaped relationships to the membrane potential with maximums around 0 mV. There was a variable latency (40-730 ms, average 230 ms) between the onset of the depolarisation and the amperometric current. During high-frequency repetitive stimulation, a progressive decrease in the exocytotic capacity ("depression") was observed. This was paralleled by a corresponding reduction of the amperometric responses. Using the carbon fibre to map the beta-cen for release sites indicated that exocytosis was confined to the part of the cell containing the highest density of secretory granules. Two types of amperometric responses were observed. In about 50% of the cells, a smooth increase was observed with no discernible discrete events. In the remaining cells. the amperometric records contained large spikes. These were ten or more times larger than that expected for the fusion of individual secretory granules. We propose that three large spikes reflect the exocytosis of multigranular complexes formed inside the beta-cell prior to exocytosis.