Lesnefsky E J, Tandler B, Ye J, Slabe T J, Turkaly J, Hoppel C L
Department of Medicine, Department of Veterans Affairs Medical Center, Cleveland, Ohio, USA.
Am J Physiol. 1997 Sep;273(3 Pt 2):H1544-54. doi: 10.1152/ajpheart.1997.273.3.H1544.
The effect of myocardial ischemia on mitochondrial oxidative phosphorylation was investigated using isolated, buffer-perfused rabbit hearts. After 45 min of global ischemia, oxidative phosphorylation was decreased only in the subsarcolemmal population of mitochondria with all substrates tested. The oxidation of N,N,N',N' tetramethyl p-phenylenediamine-ascorbate, an electron donor to cytochrome oxidase via cytochrome c, was decreased in subsarcolemmal mitochondria [ischemia (n = 6): 76 +/- 3 vs. control (n = 5): 105 +/- 6 nanoatoms O.min-1.mg-1, P < 0.01] but not in interfibrillar mitochondria. Only minor morphological changes were observed by electron microscopy in the isolated mitochondria after ischemia. Neither cytochrome oxidase activity measured under conditions for maximal activity nor the apparent Michaelis constant and maximum velocity values of the two cytochrome c binding sites were different in subsarcolemmal mitochondria isolated from ischemic and control hearts. The cytochrome c content was decreased in subsarcolemmal mitochondria after ischemia (ischemia: 0.111 +/- 0.013 vs. control: 0.156 +/- 0.007 nmol/mg protein, P < 0.05). Thus ischemia decreased the rate of oxidative phosphorylation through cytochrome oxidase selectively in intact subsarcolemmal mitochondria. Ischemic damage to the terminal segment of the electron transport chain involves a decrease in the content of cytochrome c, whereas the expressible catalytic activity of cytochrome oxidase remains unchanged.
利用离体的、缓冲液灌注的兔心脏研究了心肌缺血对线粒体氧化磷酸化的影响。在全心缺血45分钟后，对于所有测试的底物，仅肌膜下线粒体群体中的氧化磷酸化降低。N，N，N'，N'-四甲基对苯二胺 - 抗坏血酸盐（一种通过细胞色素c向细胞色素氧化酶提供电子的供体）在肌膜下线粒体中的氧化减少[缺血组（n = 6）：76±3 vs. 对照组（n = 5）：105±6纳原子氧·分钟⁻¹·毫克⁻¹，P <0.01]，但在肌原纤维间线粒体中未减少。缺血后，通过电子显微镜观察分离的线粒体仅发现轻微的形态学变化。从缺血和对照心脏分离的肌膜下线粒体中，在最大活性条件下测得的细胞色素氧化酶活性以及两个细胞色素c结合位点的表观米氏常数和最大速度值均无差异。缺血后肌膜下线粒体中的细胞色素c含量降低（缺血组：0.111±0.013 vs. 对照组：0.156±0.007 nmol/毫克蛋白，P <0.05）。因此，缺血选择性地降低了完整肌膜下线粒体中通过细胞色素氧化酶的氧化磷酸化速率。电子传递链末端段的缺血性损伤涉及细胞色素c含量的降低，而细胞色素氧化酶的可表达催化活性保持不变。
