Akopova O V, Sagach V F
Ukr Biokhim Zh (1999). 2004 Jan-Feb;76(1):48-55.
The mitochondrial role opening (MPT) induced by Ca2+ has been studied in isolated rat heart mitochondria. MPT was characterized as cyclosporine A-inhibited swelling accompanied by the loss of membrane potential (deltapsim) and Ca2+ efflux after the Ca2+ -loading which was followed spectrophotometrically after the Ca2+ -arsenaso-III complex formation. It has been shown that in suspension of isolated mitochondria MPT was activated by low (with maximum at about 20 microM Ca2+) and high concentrations of Ca2+ (the concentration curve shows a saturation at about 1.0-1.5 mM). In all the cases an access of Ca2+ ions to the matrix space of the mitochondria was necessary for MPT induction. MPT activated by low concentrations of Ca2+ was accompanied by slow decrease of deltapsim and slow release of Ca2+, enhanced by ruthenium red (RR), and was independent of the substrate used (glutamate or succinate). It had not been observed if the respiratory chain was inhibited, even if the Ca2+ access to the inner mitochondrial membrane was provided by Ca2+ -ionophore A23187. At high Ca2+ concentrations rapid Ca2+ -uptake and release via Ca2+ -uniporter (inhibited by ruthenium red) followed by extensive swelling (pore formation) have been observed. It had been supposed that rapid MPT at high concentrations of Ca2+ was the result of Ca2+ entrance to the mitochondrial matrix and depolarisation of the mitochondrial membrane. The data obtained show two different mechanisms of Ca2+ -induced MPT. The one is sensitive to the redox-state of the electron transport chain and is abolished if the respiration is inhibited. The other is independent of mitochondrial respiration and needs only Ca2+ access to the inner mitochondrial membrane and Ca2+ binding to some specific sites leading to MPT opening.
已在分离的大鼠心脏线粒体中研究了由Ca2+诱导的线粒体通透性转换孔（MPT）。MPT的特征是环孢菌素A抑制的肿胀，伴随着膜电位（Δψm）的丧失以及Ca2+加载后Ca2+外流，Ca2+加载后通过分光光度法跟踪Ca2+ -arsenaso-III复合物的形成。结果表明，在分离的线粒体悬浮液中，低浓度（最大值约为20μM Ca2+）和高浓度的Ca2+（浓度曲线在约1.0 - 1.5 mM处显示饱和）均可激活MPT。在所有情况下，Ca2+离子进入线粒体基质空间是诱导MPT所必需的。低浓度Ca2+激活的MPT伴随着Δψm的缓慢下降和Ca2+的缓慢释放，钌红（RR）可增强这种释放，且与所使用的底物（谷氨酸或琥珀酸）无关。即使通过Ca2+离子载体A23187使Ca2+进入线粒体内膜，若呼吸链受到抑制，也未观察到MPT。在高Ca2+浓度下，观察到通过Ca2+单向转运体（受钌红抑制）快速摄取和释放Ca2+，随后出现广泛肿胀（孔形成）。据推测，高浓度Ca2+时快速的MPT是Ca2+进入线粒体基质和线粒体膜去极化所致。所获得的数据显示了Ca2+诱导MPT的两种不同机制。一种对电子传递链的氧化还原状态敏感，若呼吸受到抑制则被消除。另一种与线粒体呼吸无关，仅需要Ca2+进入线粒体内膜并与某些特定位点结合导致MPT开放。
