Nakazaki M, Ishihara H, Kakei M, Inukai K, Asano T, Miyazaki J I, Tanaka H, Kikuchi M, Yada T, Oka Y
First Department of Internal Medicine, Faculty of Medicine, Kagoshima University, Japan.
Diabetologia. 1998 Mar;41(3):279-86. doi: 10.1007/s001250050904.
We examined the relationship between cytosolic Ca2+ concentration ([Ca2+]c) and mitochondrial matrix Ca2+ concentration ([Ca2+]m) in the pancreatic beta-cell line, MIN6. [Ca2+]c was monitored in a single or a group (30 cells) of fura-2-loaded MIN6 cells, and [Ca2+]m was measured in a group (1 x 10[6] cells) of MIN6 cells stably transfected with aequorin targeted at the mitochondria. Exogenous ATP (0.25 mmol/l) produced a single transient increase in [Ca2+]c whereas 22 mmol/l KCl produced a sustained plateau increase. ATP and KCl evoked transient increases in [Ca2+]m but with distinct time courses of [Ca2+]m decline: the [Ca2+]m increase induced by ATP decreased more rapidly than that induced by KCl. Nitrendipine (3 micromol/l), a blocker of L-type Ca2+ channels, inhibited both [Ca2+]c and [Ca2+]m signals in response to KCl and tolbutamide, but not those to ATP. Peak levels of [Ca2+]m increase (around 2 micromol/ l) exceeded those of [Ca2+]c increase (around 500 nmol/l). A rise in glucose concentration from 3 to 30 mmol/l induced oscillations of [Ca2+]c that overlay the sustained increases in [Ca2+]c in single cells. An oscillatory increase in [Ca2+]m was similarly observed in response to glucose. Addition of 10 mmol/l 2-ketoisocaproic acid at 20 mmol/l glucose further increased the plateau level of [Ca2+]c and the frequency of [Ca2+]c oscillations, which were correlated with a further increase in [Ca2+]m. In response to pulsatile exposure to KCl, [Ca2+]c and [Ca2+]m increased synchronously. These data suggest that an oscillatory increase in [Ca2+]m in beta cells, the signal which is thought to be necessary for continuous stimulation of mitochondrial metabolism, is produced synchronously with the [Ca2+]c oscillations.
我们研究了胰腺β细胞系MIN6中胞质Ca2+浓度（[Ca2+]c）与线粒体基质Ca2+浓度（[Ca2+]m）之间的关系。在单个或一组（30个细胞）负载fura-2的MIN6细胞中监测[Ca2+]c，在稳定转染了靶向线粒体的水母发光蛋白的一组（1×10[6]个细胞）MIN6细胞中测量[Ca2+]m。外源性ATP（0.25 mmol/l）使[Ca2+]c产生单次短暂升高，而22 mmol/l KCl使[Ca2+]c产生持续的平台期升高。ATP和KCl引起[Ca2+]m短暂升高，但[Ca2+]m下降的时间进程不同：ATP诱导的[Ca2+]m升高比KCl诱导的下降更快。L型Ca2+通道阻滞剂尼群地平（3 μmol/l）抑制了对KCl和甲苯磺丁脲的[Ca2+]c和[Ca2+]m信号，但不抑制对ATP的信号。[Ca2+]m升高的峰值水平（约2 μmol/l）超过了[Ca2+]c升高的峰值水平（约500 nmol/l）。葡萄糖浓度从3 mmol/l升高到30 mmol/l会诱导[Ca2+]c振荡，该振荡叠加在单个细胞中[Ca2+]c的持续升高之上。类似地，在对葡萄糖的反应中观察到[Ca2+]m的振荡性升高。在20 mmol/l葡萄糖时添加10 mmol/l 2-酮异己酸进一步增加了[Ca2+]c的平台期水平和[Ca2+]c振荡的频率，这与[Ca2+]m的进一步增加相关。在对脉动性暴露于KCl的反应中，[Ca2+]c和[Ca2+]m同步增加。这些数据表明，β细胞中[Ca2+]m的振荡性升高与[Ca2+]c振荡同步产生，而[Ca2+]m振荡被认为是持续刺激线粒体代谢所必需的信号。
