Hüser J, Rechenmacher C E, Blatter L A
Department of Physiology, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153, USA.
Biophys J. 1998 Apr;74(4):2129-37. doi: 10.1016/S0006-3495(98)77920-2.
In mitochondria the opening of a large proteinaceous pore, the "mitochondrial permeability transition pore" (MTP), is known to occur under conditions of oxidative stress and matrix calcium overload. MTP opening and the resulting cellular energy deprivation have been implicated in processes such as hypoxic cell damage, apoptosis, and neuronal excitotoxicity. Membrane potential (delta psi(m)) in single isolated heart mitochondria was measured by confocal microscopy with a voltage-sensitive fluorescent dye. Measurements in mitochondrial populations revealed a gradual loss of delta psi(m) due to the light-induced generation of free radicals. In contrast, the depolarization in individual mitochondria was fast, sometimes causing marked oscillations of delta psi(m). Rapid depolarizations were accompanied by an increased permeability of the inner mitochondrial membrane to matrix-entrapped calcein (approximately 620 Da), indicating the opening of a large membrane pore. The MTP inhibitor cyclosporin A significantly stabilized delta psi(m) in single mitochondria, thereby slowing the voltage decay in averaged recordings. We conclude that the spontaneous depolarizations were caused by repeated stochastic openings and closings of the transition pore. The data demonstrate a much more dynamic regulation of membrane permeability at the level of a single organelle than predicted from ensemble behavior of mitochondrial populations.
在线粒体中，一种大型蛋白质孔道“线粒体通透性转换孔”（MTP）的开放已知会在氧化应激和基质钙超载的情况下发生。MTP的开放以及由此导致的细胞能量剥夺与诸如缺氧细胞损伤、凋亡和神经元兴奋毒性等过程有关。通过使用电压敏感荧光染料的共聚焦显微镜测量单个分离的心脏线粒体中的膜电位（Δψm）。对线粒体群体的测量显示，由于光诱导的自由基产生，Δψm逐渐丧失。相比之下，单个线粒体中的去极化很快，有时会导致Δψm出现明显振荡。快速去极化伴随着线粒体内膜对基质包裹的钙黄绿素（约620 Da）的通透性增加，表明有一个大的膜孔开放。MTP抑制剂环孢素A显著稳定了单个线粒体中的Δψm，从而减缓了平均记录中的电压衰减。我们得出结论，自发去极化是由转换孔的反复随机开放和关闭引起的。数据表明，在单个细胞器水平上，膜通透性的调节比从线粒体群体的整体行为预测的要动态得多。
