烧伤后大鼠不同类型骨骼肌蛋白降解率的变化规律及其与糖皮质激素间的关系

CHANGES IN PROTEOLYTIC RATE OF DIFFERENT KINDS OF SKELETAL MUSCLE FOLLOWING BURN INJURY AND ITS RELATIONSHIP WITH GLUCOCORTICOID

为了解烧伤后不同类型骨骼肌蛋白降解率和血浆中糖皮质激素含量的变化 ,比较不同类型骨骼肌对烧伤刺激的反应 ,分析烧伤后骨骼肌萎缩的调节因子 ,应用 30 %Ⅲ度烫伤大鼠模型 ,借助骨骼肌充分氧供离体孵育系统 ,采用氨基酸全谱分析仪测定大鼠伤后不同时间点伸趾长肌和比目鱼肌蛋白降解率 ,用放射免疫分析测定大鼠血浆中糖皮质激素含量。结果发现 :烧伤后大鼠伸趾长肌总蛋白降解率和肌纤维蛋白降解率均明显增加 ,以烧伤后 12h和 2 4h为著 ,其中肌纤维蛋白降解率增幅明显 ;比目鱼肌总蛋白降解率和肌纤维蛋白降解率烧伤后均无显著变化 ;烧伤后不同时间点血浆糖皮质激素含量较正常对照组均显著增加 (P <0 0 1) ;伸趾长肌蛋白降解率与血浆糖皮质激素增加密切相关。说明烧伤后骨骼肌萎缩主要是由于肌纤维蛋白大量降解所致 ,快白肌比慢红肌对烧伤刺激敏感 ;糖皮质激素可能是导致骨骼肌蛋白降解增强的重要调节因子。

To observe the changes in proteolytic rate of different kinds of skeletal muscle and the content of serum glucocorticoid in rats after burn injury,to compare the response of different types of skeletal muscle to burn injury,and to preliminarily investigate the factors modulating skeletal muscle proteolysis after burn injury, Wistar rats were inflicted 30%TBSA(total body surface area) full-thickness burn. The rats were randomly divided into 4 groups as the following: 2h, 6h, 12h and 24h after burn injury, each time point was matched with a sham control group. In-vitro muscle incubation system with sufficient oxygen supply as well as amino acid automatic analyzer were used for the assessment of the proteolytic rate of extensor digitorium longus(EDL) and soleus(SOL)muscles. The level of serum glucocorticoid was determined with radio-immuno assay. The result indicated that total proteolytic rate and myofibrillar proteolytic rate in EDL muscle increased strikingly at each time point after burn injury, and the rise of myofibrillar proteolytic rate was even greater in magnitude. No statistically significant difference in total and myofibrillar proteolytic rate occurred in SOL muscle during postburn period. Serum glucocorticoid notably increased in each observation time point compared with that of normal control( P <0 01). A significant positive correlation between the myofibrillar proteolytic rate of skeletal muscle and plasma concentration of glucocorticoid existed.Muscle wasting of burn injury was primarily due to enhancement of myofibrillar proteolysis, and fast-white muscle is more sensitive to burn injury than slow-red muscle. Glucocorticoid is probably the important mediator of skeletal muscle proteolysis.