Involvement of mitochondrial Na+–Ca2+ exchange in intracellular Ca2+ increase induced by ATP in PC12 cells
Involvement of mitochondrial Na+–Ca2+ exchange in intracellular Ca2+ increase induced by ATP in PC12 cells
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DOI：
10.1016/j.brainres.2004.03.042
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发表时间：
2004-07
期刊：
影响因子：
2.9
通讯作者：
K. Maruyama;T. Ohta;S. Ito
中科院分区：
文献类型：
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作者：
K. Maruyama;T. Ohta;S. Ito
在大鼠嗜铬细胞瘤(PC)12细胞中，观察了线粒体Na~+-Ca~(2+)交换在Ca~(2+)对ATP的反应中的作用。Fura-2和SBFI分别测定细胞内钙离子浓度([Ca+]i)和钠离子浓度([Na+]i)。ATP引起PC12细胞内[Ca~(2+)]_i和[Na~+]_i浓度依赖性升高。高浓度的ATP可引起77%的PC12细胞内钙瞬变，随后[Ca~(2+)]_i缓慢恢复。只有当峰值钙瞬变超过500 nM时，才出现钙反应的持续期。FCCP是一种原生生物，只有在有持续时相的细胞中才能显著增强细胞对ATP的钙反应，而不是在没有持续时相的细胞中。氯硝西潘和CGP37157、线粒体Na+-Ca~(2+)交换抑制剂和细胞外Na~+清除可使缓释期减少，而通透性转换孔抑制剂环孢素A则不能。在无Na+的情况下，ATP刺激3.5min后再注入Na+可引起线粒体[Ca~(2+)]_i和[Na~+]_i呈浓度依赖性的升高，[Na~+]_i的升高与[Ca~(2+)]_i的升高呈正相关，而FCCP在无Na~+的情况下使细胞内[Ca~(2+)]_i显著升高，说明线粒体在无Na~+的情况下仍能保留钙离子。这些结果表明，ATP引起线粒体内游离钙离子浓度的显著升高，线粒体对ATP反应的持续时相主要是由于线粒体通过Na+-Ca~(2+)交换器释放钙离子所致。
The involvement of mitochondrial Na+–Ca2+exchange in Ca2+responses to ATP was examined in rat pheochromocytoma (PC) 12 cells. Intracellular Ca2+([Ca2+]i) and Na+concentrations ([Na+]i) were measured using fura-2 and SBFI, respectively. ATP caused concentration-dependent increases in [Ca2+]iand [Na+]i. High concentrations of ATP elicited a Ca2+transient followed by a slow recovery of [Ca2+]i(a sustained phase) in 77% of PC12 cells. The sustained phase of Ca2+response appeared only when the peak Ca2+transient exceeded 500 nM. FCCP, a protonophore, greatly enhanced Ca2+responses to ATP only in cells with the sustained phase but not without this phase. The sustained phase was decreased by clonazepam and CGP37157, mitochondrial Na+–Ca2+exchange inhibitors, and extracellular Na+removal but not by cyclosporin A, an inhibitor of permeability transition pores. The reintroduction of Na+3.5 min after ATP stimulation in the absence of Na+caused Na+concentration-dependent increases in [Ca2+]iand [Na+]i. The increase in [Na+]iwas correlated with that in [Ca2+]i. FCCP caused a great increase in [Ca2+]i4.5 min after ATP stimulation in the absence of extracellular Na+but not in its presence, indicating that mitochondria retain Ca2+in the absence of Na+. These results suggest that ATP causes a large increase in [Ca2+]iwhich was sequestered in mitochondria and that the sustained phase of Ca2+response to ATP are mainly due to the release of mitochondrial Ca2+through Na+–Ca2+exchangers in PC12 cells.