Nishimura M, Takami H, Kaneko M, Nakano S, Matsuda H, Kurosawa K, Inoue T, Tagawa K
First Department of Surgery, Osaka University Medical School, Suita, Japan.
Cardiovasc Res. 1993 Jun;27(6):1116-22. doi: 10.1093/cvr/27.6.1116.
The aim was to clarify the factors that induce enzyme release from mitochondria during anoxia and reoxygenation.
Isolated perfused hearts or isolated mitochondria were prepared from hearts excised from rats. The amounts of lactate dehydrogenase, cytoplasmic aspartate aminotransferase, and mitochondrial aspartate aminotransferase released into the coronary effluent from perfused heart preparations were measured. To distinguish the effect of mechanical stress from that of reoxygenation, a latex balloon was placed in the left ventricular cavity to impose mechanical stress and the heartbeat was controlled with a high K+ medium. A digitonin infusion technique was used to obtain only the cytosolic compartment of the cells for analysis of the amounts of mitochondrial enzymes released into the cytosol. The effect of anoxia followed by reoxygenation on enzyme release from isolated mitochondria was studied.
On reoxygenation, mitochondrial aspartate aminotransferase was released as well as cytoplasmic enzymes, but, unlike cytoplasmic enzymes, the release was not influenced by mechanical stress. Mitochondrial injury by reoxygenation depended on the duration of the preceding anoxia. Reoxygenation of isolated mitochondria also induced enzyme release and the presence of ATP in the extramitochondrial space reduced the release of this enzyme.
Enzyme leakage from mitochondria of myocardial cells occurs during reoxygenation, irrespective of mechanical stress, and this vulnerability to oxidative stress depends on the duration of the preceding anoxic period or the concentration of cytosolic ATP.
本研究旨在阐明缺氧及复氧过程中诱导线粒体释放酶的因素。
从大鼠心脏分离制备离体灌注心脏或离体线粒体。测定灌注心脏标本冠脉流出液中乳酸脱氢酶、胞质天冬氨酸氨基转移酶和线粒体天冬氨酸氨基转移酶的释放量。为区分机械应激与复氧的影响，在左心室腔内置入乳胶气球施加机械应激，并用高钾培养基控制心跳。采用洋地黄皂苷注入技术仅获取细胞的胞质部分，以分析释放到胞质中的线粒体酶量。研究缺氧后复氧对离体线粒体酶释放的影响。
复氧时，线粒体天冬氨酸氨基转移酶与胞质酶一同释放，但与胞质酶不同，其释放不受机械应激影响。复氧所致的线粒体损伤取决于先前缺氧的持续时间。离体线粒体复氧也诱导致酶释放，线粒体外空间中ATP的存在可减少该酶的释放。
心肌细胞线粒体在复氧过程中会发生酶泄漏，与机械应激无关，且这种对氧化应激的易感性取决于先前缺氧期的持续时间或胞质ATP的浓度。
