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目的探讨＋ＧＺ负荷致大鼠膈肌收缩性能下降的原因。方法观察＋ＧＺ负荷后大鼠膈肌ＡＴＰ酶活性的变化。将２０只成年雄性ＳＤ大鼠随机分为对照组和＋ＧＺ负荷组（＋ＧＺ负荷量为：＋４ＧＺ始，每上升＋１ＧＺ持续３ｍｉｎ，至＋１０ＧＺ止，总负荷时间为２１ｍｉｎ）。所有动物均猛击头部后迅速剖开胸腹，取右半侧膈肌制成肌肉卷并即刻浸入液氮中冷冻。将冰冻肌肉条切成１０μｍ厚切片，以钙钴法进行ＡＴＰ酶染色，对染色切片进行图像分析，测定Ⅰ型和Ⅱ型纤维的面积及ＡＴＰ酶光密度。结果两组动物在膈肌纤维组成上没有显著性差异（Ｐ＞０．０５），而＋ＧＺ负荷后各型纤维的ＡＴＰ酶活性均有下降（Ｐ＜０．０５），尤以Ⅰ型纤维为著（Ｐ＜０．０１）。结论急性＋ＧＺ负荷条件下，大鼠膈肌肌球蛋白ＡＴＰ酶活性下降是膈肌收缩性能改变的原因之一。
Objective To investigate the reason of the decrease of diaphragmatic contractility induced by + GZ in rats. Methods The changes of ATPase activity of diaphragm in rats after + GZ stress were observed. Twenty adult male Sprague-Dawley rats were randomly divided into control group and + GZ load group (+ GZ load: + 4GZ for each rise + 1GZ for 3min to + 10GZ, the total load time was 21min). All animals swiftly cut their chest and abdomen after smashing their heads, made a muscle roll from the right half of the diaphragm and immediately immerse them in liquid nitrogen for freezing. Frozen muscle strips were cut into 10μm thick sections, and ATPase staining was performed by calcium-cobalt method. The stained sections were analyzed by image analysis to determine the area of type I and type II fibers and the optical density of ATPase. Results There was no significant difference (P> 0.05) between the two groups in the composition of diaphragmatic muscle fibers, and the ATPase activity of all kinds of fibers after + GZ stress decreased (P <0.05), especially type Ⅰ fibers (P <0.01). Conclusion Under the condition of acute + GZ stress, the decrease of diaphragmatic myosin ATPase activity is one of the reasons for the change of diaphragmatic contractility.