Bhattacharya S K, Johnson P L, Thakar J H
Edward Dana Mitchell Surgical Research Laboratories, University of Tennessee Medical Center, Memphis 38163, USA.
Mol Chem Neuropathol. 1998 May;34(1):53-77. doi: 10.1007/BF02815136.
Membrane-mediated excessive intracellular calcium accumulation (EICA) and diminished cellular energy production are the hallmarks of dystrophic pathobiology in Duchenne and Becker muscular dystrophies. We reported reversal of respiratory damage and Ca(2+)-overloading in the in vitro cardiac mitochondria from CHF-146 dystrophic hamsters (DH) with hereditary muscular dystrophy (Bhattacharya et al., 1993). Here we studied respiratory dysfunctions in the skeletal muscle mitochondria from young and old DH, and whether these abnormalities can be reversed by reducing [Ca2+] in the isolation medium, thereby lowering intramitochondrial Ca(2+)-overloading. Age- and sex-matched CHF-148 albino normal hamsters (NH) served as controls. As an index of EICA and cellular degeneration, Ca and Mg levels were assayed in the skeletal muscle and mitochondria. Mitochondria from young and old DH, isolated without EDTA (BE medium), revealed poor coupling of oxidative phosphorylation, diminished stimulated oxygen consumption rate, and lower respiratory control ratio and ADP/O ratios, compared to NH. Incorporation of 10 mM EDTA (Bo medium) in the isolation medium restored mitochondrial functions of the dystrophic organelles to a near-normal level, and reduced Ca(2+)-overloading. The mitochondrial Ca level in DH was significantly higher than in NH, irrespective of the medium. However, compared to Bo medium, the dystrophic organelles isolated in BE medium had lower Ca levels and markedly improved oxidative phosphorylation as seen in NH. Muscle Ca contents in the young and old DH were elevated relative to NH, showing a positive correlation with the increased mitochondrial Ca(2+)-sequestration. Dystrophic muscle also revealed Ca deposition with an abundance of Ca(2+)-positive and necrotic myofibers by light microscopy, and intramitochondrial Ca(2+)-overloading by electron microscopy, respectively. However, Mg levels in the muscle and mitochondria did not alter with age or dystrophy. These data parallel our observations in the heart, and suggest that functional impairments and Ca(2+)-overloading also occur in the skeletal muscle mitochondria of DH, and are indeed reversible if EICA is regulated by slow Ca(2+)-channel blocker therapy (Johnson and Bhattacharya, 1993).
膜介导的细胞内钙过度积累（EICA）和细胞能量产生减少是杜兴氏和贝克氏肌肉营养不良症营养不良病理生物学的标志。我们报道了遗传性肌肉营养不良的CHF - 146营养不良仓鼠（DH）体外心脏线粒体中呼吸损伤和Ca(2+)超载的逆转（Bhattacharya等人，1993年）。在这里，我们研究了年轻和老年DH骨骼肌线粒体中的呼吸功能障碍，以及这些异常是否可以通过降低分离培养基中的[Ca2+]来逆转，从而降低线粒体内Ca(2+)超载。年龄和性别匹配的CHF - 148白化正常仓鼠（NH）作为对照。作为EICA和细胞变性的指标，测定了骨骼肌和线粒体中的钙和镁水平。与NH相比，在没有EDTA（BE培养基）的情况下分离的年轻和老年DH的线粒体显示出氧化磷酸化的偶联不良、刺激的氧消耗率降低以及较低的呼吸控制率和ADP/O比率。在分离培养基中加入10 mM EDTA（Bo培养基）可将营养不良细胞器的线粒体功能恢复到接近正常水平，并减少Ca(2+)超载。无论培养基如何，DH中的线粒体钙水平均显著高于NH。然而，与Bo培养基相比，在BE培养基中分离的营养不良细胞器的钙水平较低，并且如在NH中所见，氧化磷酸化明显改善。年轻和老年DH中的肌肉钙含量相对于NH升高，与线粒体Ca(2+)螯合增加呈正相关。营养不良肌肉通过光学显微镜还显示钙沉积，有大量Ca(2+)阳性和坏死肌纤维，通过电子显微镜显示线粒体内Ca(2+)超载。然而，肌肉和线粒体中的镁水平不会随年龄或营养不良而改变。这些数据与我们在心脏中的观察结果相似，并表明DH的骨骼肌线粒体中也发生功能损害和Ca(2+)超载，并且如果通过慢Ca(2+)通道阻滞剂疗法调节EICA，这些损害确实是可逆的（Johnson和Bhattacharya，1993年）。
