中文摘要：

目的观察电离辐射对大鼠咬肌细胞Ca^2＋ - Mg^2＋ - ATP酶（钙泵）活性和表达的影响，从细胞内钙调节角度探讨电离辐射引起肌肉损伤的机制。方法将Sprague—Dawley大鼠分为两组，照射组16只，对照组12只。一次性20Gyx射线局部照射大鼠咬肌区，化学比色法检测照射后大鼠咬肌Ca^2＋ - Mg^2＋ - ATP酶活性的变化；蛋白质印迹法和免疫组织化学检测咬肌Ca^2＋ - Mg^2＋ - ATP酶表达的变化。结果照射后3d大鼠咬肌Ca^2＋ - Mg^2＋ - ATP酶活性[（5．61±0．93）μmol（磷）·mg^-1（蛋白）·h^-1]降低约20％；照射后30d[（4．75±0．58）μmol（磷）·mg^-1（蛋白）·h^-1]降低40％；照射后30d，大鼠照射组与对照组比较，差异有统计学意义（P〈0．01）。Ca^2＋ - Mg^2＋ - ATP酶主要表达在细胞质，与肌浆网的位置相一致。照射后大鼠咬肌Ca^2＋ - Mg^2＋ - ATP酶表达无明显变化。结论照射后肌纤维Ca^2＋ - Mg^2＋ - ATP酶活性下降可能是电离辐射引起肌肉损害的一个重要因素。Ca^2＋ - Mg^2＋ - ATP酶活性降低不是由于其数量减少所致，而是由于Ca^2＋ - Mg^2＋ - ATP酶本身功能异常造成的。

英文摘要：

Objective To investigate the activity and expression of Ca^2＋ - Mg^2＋ - ATPase in irradiated rat masseter muscle. Methods The rats were irradiated locally with a single dose of 20 Gy X- ray. The activities of Ca^2＋ - Mg^2＋ - ATPase were measured with calorimetric method. The protein expression of Ca^2＋ - Mg^2＋ - ATPase was determined by Western blotting and immunohistochemistry. Results The activities of Ca^2＋ - Mg^2＋ - ATPase in masseter muscle decreased by approximately 20% and 40% in irradiated rats on days 3 and 30 postirradiation. There was significant difference in the expression of Ca^2＋ - Mg^2＋ - ATPase protein between irradiated and nonirradiated rats on day 30 postirradiation. Ca^2＋ - Mg^2＋ - ATPase protein was found in the cytoplasm of masseter muscle. Conclusions The decrease of ATPase activity played an important role in the cause of radiation-induced skeletal muscle injury, while there was no reduction in the expression of Ca^2＋ - Mg^2＋ - ATPase protein in irradiated rat masseter muscle