氟美松对正常大鼠膈肌的影响

EXPERIMENTAL STUDIES ABOUT EFFECT OF DEXAMETHASONE ON DIAPHRAGM OF NORMAL RATS

利用氟美松制备的大鼠类固醇肌病模型，研究了氟美松对大鼠膈肌的重量、收缩特性、肌纤维的横断面积、氧化酶活性、糖原和超微结构的影响。结果发现：（１）氟美松的使用可使大鼠膈肌明显萎缩，以Ⅱａ、Ⅱｂ型纤维萎缩为著；（２）在１００Ｈｚ电刺激下，膈肌的张力明显下降，膈肌耐疲劳的能力（１／２ＲＴ）显著提高；（３）膈肌中Ⅰ型、Ⅱｂ型纤维中ＡＴＰ酶、琥珀酸脱氢酶（ＳＤＨ）的活性均下降，膈肌中糖原含量增加。电镜观察发现氟美松可以导致膈肌线粒体增生、空泡样变性及部分肌丝局灶性破坏。氟美松导致的上述各种改变，可能直接或间接地影响膈肌物质能量代谢而导致其收缩性能的改变。

The influence of dexamethasone on diaphragm function, its oxidative capacity, fiber cross sectional areas, the content of glycogen and ultrastructural changes were determined in Wistar rats by receiving dexamethasone (2mg/kg) muscle injection for two weeks. We noted dexamethasone treatment leads to significant atrophy of the mass of diaphragm, reduction of fiber cross sectional areas (CSA) of type Ⅱa, Ⅱb fibers. Under high frequency (100Hz) stimulation, the tention of the diaphragm muscle strips was decreased and diaphragm fatigue resistance (1/2 RT) was significantly improved. Histochemically, ATPase activity in type Ⅰ and type Ⅱb fibers of the diaphragm was significantly reduced and a significant reduction of succinate dehydrogenase activity in the diaphragm was also observed, but increased glycogen was seen in the diaphragm. Ultrastructural changes including mitochondrial hyperplasia, swelling, myofibillae focus destructure were evident. It is concluded that steroid induced myopathy may also involve the diaphragm.