Kargacin M E, Kargacin G J
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Biochim Biophys Acta. 1996 May 21;1290(1):4-8. doi: 10.1016/0304-4165(95)00180-8.
In Duchenne muscular dystrophy, muscle cells, which lack the protein dystrophin, have been reported to have elevated resting intracellular calcium levels. It has also been noted that, compared to normal muscle, intracellular [Ca2+] in dystrophic muscle returns more slowly to its resting level following contractile stimulation. Consistent with this, it has been suggested that dystrophin is directly involved in the regulation of Ca2+ influx. A secondary alteration in the sarcoplasmic reticulum Ca2+ pump, however, could also contribute to, or be responsible for, the abnormal Ca2+ handling seen. To determine whether the Ca2+ pump is functionally altered in dystrophic muscle, we examined Ca2+ uptake by vesicles derived from skeletal muscle sarcoplasmic reticulum of normal and dystrophic (mdx) mice. The Hill coefficient and the Ca2+ sensitivity of the Ca2+- ATPase were the same in both cases. The maximum velocity of Ca2+ uptake, however, normalized to the ATPase content of the vesicles, was less for mdx muscle.
在杜兴氏肌营养不良症中，据报道缺乏抗肌萎缩蛋白的肌肉细胞静息时细胞内钙水平升高。还注意到，与正常肌肉相比，营养不良肌肉在收缩刺激后细胞内[Ca2+]恢复到静息水平的速度更慢。与此一致的是，有人提出抗肌萎缩蛋白直接参与Ca2+内流的调节。然而，肌浆网Ca2+泵的继发性改变也可能导致或引发所观察到的异常Ca2+处理。为了确定Ca2+泵在营养不良肌肉中是否功能改变，我们检测了来自正常和营养不良（mdx）小鼠骨骼肌肌浆网的囊泡对Ca2+的摄取。两种情况下Ca2+-ATP酶的希尔系数和Ca2+敏感性相同。然而，以囊泡的ATP酶含量进行标准化后，mdx肌肉的Ca2+摄取最大速度较低。
