Chai Jiake, Shen Chuan'an, Sheng Zhiyong
Burns Institute, The 304th Hospital of People's Liberation Army, Beijing, 100037, China.
Zhonghua Wai Ke Za Zhi. 2002 Sep;40(9):705-8.
To study the effects of glucocorticoid on skeletal muscle protein metabolism in burn sepsis and its possible mechanism.
The rats were randomly divided into four groups with 15 rats in each group. Group B, 30% TBSA full-thickness burn was produced on the back and endotoxin (6 mg/kg bw) was given intraperitoneally after the injury to simulate burn sepsis. Groups C and D, glucocorticoid receptor antagonist RU38486 (10 mg/kg bw) was given by gavage 2 hours before or 2 hours after burn with endotoxin, respectively. Group A, the rats received only normal saline in same volume as endotoxin. Plasma levels of cortisol were determined with standard procedure. Extensor digitorium longus muscles (EDL) were procured from both legs 12 hours after the injury. After weighing, the proteolytic rate was determined in vitro in an incubation system with oxygen rich environment by high performance liquid chromatography. The gene expressions of ubiquitin, E(2)-14kDa and C2 in the muscles were determined by Northern blot analysis.
The weight of EDL was significantly lower in group B than in group A (t = 9.03, P < 0.01). Although the weight of EDL muscles was also lower in groups C and D than in group A, it was significantly higher than in group B (t = 2.26, 6.42, P < 0.05 or P < 0.01). The concentrations of plasma cortisol were markedly higher in groups B, C and D than in group A (t = 9.03 - 22.94, P < 0.01). A 58.8% (210/357) of the total and 335.5% (4.16/1.24) of myofibrillar proteolytic rate in group B was higher than in group A (t = 36.99 and t = 46.19, P < 0.01), respectively. The total and myofibrillar proteolytic rate in group D was 28.3% (161/567) and 49.6% (2.68/5.40) and in group C 18.9% (108/567) and 23.2% (1.25/5.40), which were lower than those in group B (t = 5.34 approximately 34.68, P < 0.01), respectively. Although the expressions of ubiquitin mRNA (2.4 kb), E(2)-14 kDa mRNA (1.2 kb) and C2 mRNA in groups C and D were significantly higher than in group A, all the values were lower than those in group B (t = 3.22, 11.32, P < 0.01), especially in group C.
The proteolytic rate of skeletal muscle, especially the myofibrillar proteolytic rate, was enhanced during burn with sepsis. Hypersecretion of glucocorticoid could upgrade the gene expression of ubiquitin system, resulting in hyperdegradation of skeletal muscle protein during burn with sepsis. Glucocorticoid receptor antagonist RU38486 could decrease the hyperdegradation of skeletal muscle during burn with sepsis.
研究糖皮质激素对烧伤脓毒症时骨骼肌蛋白质代谢的影响及其可能机制。
将大鼠随机分为4组，每组15只。B组，于背部造成30%体表面积的全层烧伤，伤后腹腔注射内毒素（6mg/kg体重）以模拟烧伤脓毒症。C组和D组，分别在烧伤合并内毒素注射前2小时或后2小时经口给予糖皮质激素受体拮抗剂RU38486（10mg/kg体重）。A组，大鼠仅给予与内毒素等量的生理盐水。按标准方法测定血浆皮质醇水平。伤后12小时取双侧趾长伸肌（EDL）。称重后，在富氧环境的孵育体系中用高效液相色谱法体外测定蛋白水解率。用Northern印迹分析法测定肌肉中泛素、E(2)-14kDa和C2的基因表达。
B组EDL重量显著低于A组（t=9.03，P<0.01）。虽然C组和D组EDL肌肉重量也低于A组，但显著高于B组（t=2.26，6.42，P<0.05或P<0.01）。B、C、D组血浆皮质醇浓度显著高于A组（t=9.03 - 22.94，P<0.01）。B组总蛋白水解率的58.8%（210/357）和肌原纤维蛋白水解率的335.5%（4.16/1.24）高于A组（t=36.99和t=46.19，P<0.01）。D组总蛋白水解率和肌原纤维蛋白水解率分别为28.3%（161/567）和49.6%（2.68/5.40），C组分别为18.9%（108/567）和23.2%（1.25/5.40），均低于B组（t=5.34～34.68，P<0.01）。虽然C组和D组泛素mRNA（2.4kb）、E(2)-14kDa mRNA（1.2kb）和C2 mRNA表达显著高于A组，但均低于B组（t=3.22，1l.32，P<0.01），C组尤其低。
烧伤脓毒症时骨骼肌蛋白水解率特别是肌原纤维蛋白水解率增高。糖皮质激素分泌增多可使泛素系统基因表达上调，导致烧伤脓毒症时骨骼肌蛋白过度降解。糖皮质激素受体拮抗剂RU~38486可减轻烧伤脓毒症时骨骼肌的过度降解。
