Dynamics of calcium clearance in mouse pancreatic β-cells
Dynamics of calcium clearance in mouse pancreatic β-cells
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DOI：
10.2337/diabetes.52.7.1723
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发表时间：
2003-07-01
期刊：
影响因子：
7.7
通讯作者：
Hille, B
中科院分区：
文献类型：
--
作者：
Chen, LY;Koh, DS;Hille, B
胰腺β细胞通过调节Ca2+依赖性胰岛素分泌来维持葡萄糖稳态。几种细胞机制控制细胞内Ca2+水平，但它们在小鼠β细胞中的相对意义尚不完全清楚。我们使用光度法测量细胞质Ca2+ ([Ca2+](i))清除后短暂的动力学，去极化诱导的Ca2+进入。用thapsigargin或环吡唑酸治疗，肌内质网Ca2+- atp酶（SERCA）泵抑制剂，几乎使峰值翻倍，减缓了去极化诱导的Ca2+瞬态的衰减。通过碱化浴液、添加镧或用Li+取代Na+来抑制质膜Ca2+- atp酶（PMCA）和质膜Na+/Ca2+交换器（NCX），进一步减缓了剩余的thapsigarin不敏感的衰变。线粒体Ca2+摄取对thapsigarin预处理细胞的清除贡献不大。在正常溶液中，SERCA、PMCA和NCX转运机制合计占清除率的89%至97%。我们开发了一个定量模型，用于在广泛的[Ca2+](i)范围内去除机制的动态作用。根据我们的模型，50至64%的初始Ca2+去除是通过SERCA泵，而NCX在高[Ca2+](i)时贡献21-30%的挤出，PMCA在低[Ca2+](i)时贡献21-27%。
Pancreatic beta-cells maintain glucose homeostasis by their regulated Ca2+-dependent secretion of insulin. Several cellular mechanisms control intracellular Ca2+ levels, but their relative significance in mouse beta-cells is not fully known. We used photometry to measure the dynamics of cytosolic Ca2+ ([Ca2+](i)) clearance after brief, depolarization-induced Ca2+ entry. Treatment with thapsigargin or cyclopiazonic acid, inhibitors of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) pumps, nearly doubled the peak and slowed the decay of the depolarization-induced Ca2+ transients. The remaining thapsigargin-insensitive decay was slowed further by inhibition of the plasma membrane Ca2+-ATPase (PMCA) and plasma membrane Na+/Ca2+ exchanger (NCX) via alkalization of the bath solution, by adding lanthanum, or by substitution of Na+ with Li+. Mitochondrial Ca2+ uptake contributed little to clearance in thapsigargin-pretreated cells. Together, the SERCA, PMCA, and NCX transport mechanisms accounted for 89 to 97% of clearance in normal solutions. We developed a quantitative model for the dynamic role of removal mechanisms over a wide range of [Ca2+](i). According to our model, 50 to 64% of initial Ca2+ removal is via the SERCA pump, whereas the NCX contributes 21-30% of the extrusion at high [Ca2+](i), and the PMCA contributes 21-27% at low [Ca2+](i).