The relationship between free and total calcium concentrations in the matrix of liver and brain mitochondria
The relationship between free and total calcium concentrations in the matrix of liver and brain mitochondria
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DOI：
10.1074/jbc.m212661200
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发表时间：
2003-05-23
影响因子：
4.8
通讯作者：
Nicholls, DG
中科院分区：
文献类型：
--
作者：
Chalmers, S;Nicholls, DG
线粒体钙积累的三个连续阶段可以区分：基质脱氢酶调节，线粒体外游离钙的缓冲，最后激活的渗透性转换。这些阶段之间的关系，游离和总基质钙浓度，磷酸盐浓度进行了研究，在大鼠肝脏和脑线粒体。采用缓慢、连续的钙输注以避免推注添加的瞬时生物能量后果。肝和脑线粒体在精确的基质钙负荷下发生渗透性转变，这与输注速率无关。细胞色素c的释放先于渗透性转变。环孢菌素A在存在或不存在乙酰乙酸的情况下增强负载能力。当总基质钙从10 nmol钙/mg蛋白质增加到至少500 nmol钙/mg蛋白质时，观察到显著恒定的游离基质钙浓度在1-5 μ M范围内，如通过基质加载的fura 2-FF监测的。增加磷酸盐降低了游离基质钙和基质钙负载能力。因此，渗透性转变不是由临界基质游离钙浓度触发的。Amplex Red检测过氧化氢的速率在钙输注过程中降低，这与该模型中氧化应激在渗透性孔活化中的作用相反。在10 nmol总基质钙/mg蛋白质时，可变和缓冲基质游离钙浓度之间发生转变。无定形Ca-3（PO 4）（2）的溶度积与观察到的基质游离钙浓度一致，并且认为基质pH在维持低基质游离钙浓度方面起主要作用。
Three sequential phases of mitochondrial calcium accumulation can be distinguished: matrix dehydrogenase regulation, buffering of extramitochondrial free calcium, and finally activation of the permeability transition. Relationships between these phases, free and total matrix calcium concentration, and phosphate concentration are investigated in rat liver and brain mitochondria. Slow, continuous calcium infusion is employed to avoid transient bioenergetic consequences of bolus additions. Liver and brain mitochondria undergo permeability transitions at precise matrix calcium loads that are independent of infusion rate. Cytochrome c release precedes the permeability transition. Cyclosporin A enhances the loading capacity in the presence or absence of acetoacetate. A remarkably constant free matrix calcium concentration, in the range 1-5 muM as monitored by matrix-loaded fura2-FF, was observed when total matrix calcium was increased from 10 to at least 500 nmol of calcium/mg of protein. Increasing phosphate decreased both the free matrix calcium and the matrix calcium-loading capacity. Thus the permeability transition is not triggered by a critical matrix free calcium concentration. The rate of hydrogen peroxide detection by Amplex Red decreased during calcium infusion arguing against a role for oxidative stress in permeability pore activation in this model. A transition between a variable and buffered matrix free calcium concentration occurred at 10 nmol of total matrix calcium/mg protein. The solubility product of amorphous Ca-3(PO4)(2) is consistent with the observed matrix free calcium concentration, and the matrix pH is proposed to play the major role in maintaining the low matrix free calcium concentration.