+G_Z负荷后大鼠膈肌ATP酶活性的变化

Alteration of diaphragm myosin ATPase activity after sustained +G Z exposure in rats.

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 diaphragm contractility decrease after sustained +G Z exposure in rats. Methods Twenty male adult sprague Dawley rats were randomly devided into two groups: +G Z group and control group. Rats of +G Z group underwent sustained +G Z exposure in animal centrifuge from +4 G Z up to +10 G Z for 21 min, while those of control group did not undergo +G Z exposure but fixed in the same fixture. After G Z exposure, the rat was fallen unconcious by a sudden hit on the head, and the right hemidiaphram was taken out frozened and sectioned. The sections were stained hy calcium cobalt method. The area and optical density of myosin ATPase of type Ⅰ and type Ⅱ fiber were measured with image analysis equipment. Results The difference of type Ⅰand type Ⅱ fiber proportion between two groups was nonsignificant ( P >0.05), while optical density of myosin ATPase in rats of +G Z group was significant lower than that in controls ( P <0.01), especially type Ⅰ fiber ( P <0.01). Conclusion It was suggested that the alteration of diaphragm contratibility following sustain +G Z exposure was mainly due to the lowering of myosin ATPase activity of diaphragm in rats.