脓毒症呼吸肌蛋白降解代谢的变化

目的探讨脓毒症早期呼吸肌蛋白降解代谢变化的规律及机制。方法45只雄性Wistar大鼠随机分为烫伤组（B组）、脓毒症组（S组）及对照组（C组）。B组大鼠使用沸水致背部30％总体表面积Ⅲ度烫伤，S组大鼠以同样方法烫伤后，立即腹腔注射内毒素（6mg／kg）制成烧伤脓毒症动物模型。分别于伤后2h和6h，采用高效液相一荧光法检测胸大肌、肋间肌和膈肌内三甲基组氨酸（3-MH）的含量，Northern杂交检测泛素、蛋白酶体C2亚基mRNA表达的变化。结果S组伤后2h和6h三处肌肉组织内3．MH的含量较B组和C组均显著升高（P〈0．05），B组伤后2h胸大肌和肋间肌内3-MH的含量较C组显著升高（P〈0．05），伤后6h三处肌肉组织内3-MH的含量均较C组显著升高（P〈0．01）。S组伤后2h和6h三处肌肉组织内泛素mRNA和蛋白酶体C2亚基mRNA表达较B组和C组均显著增强（P〈0．01），B组伤后2h和6h三处肌肉组织内泛素和蛋白酶体C2亚基mRNA表达较C组均显著增强（P〈0．05）。结论严重烫伤特别是合并内毒素攻击后早期，呼吸肌细胞泛素-蛋白酶体途径活性呈现持续增强现象，肌纤维蛋白降解率也显著增加。这对于进一步从蛋白降解角度探讨烧伤脓毒症时呼吸肌功能异常的机制有参考意义。

Changes of respiratory muscle proteolysis in burn sepsis in rats

Objective To study the changes and mechanisms of respiratory muscle proteolysis in burn sepsis in rats.Methods Forty-five male Wistar rats were randomly divided into burn group(group B),burn sepsis group(group S) and control group(group C).The full-thickness burn injury involved 30% total body surface area(TBSA),and the model of burn sepsis was replicated by administration of endotoxin(6 mg/kg) into the peritoneal cavity immediately after burn injury.Two and six hours post-injury,contents of 3-methylhistidine in pectoralis major muscle,intercostal muscle and diaphragmatic muscle were determined with high performance liquid chromatography.The expressions of ubiquitin mRNA and C_2 subunit mRNA in those muscles were assessed with Northern blot analysis.Results The contents of 3-MH in all muscles of rats in group S increased significantly at 2 hr and 6 hr compared with rats in group B and C(all P<0.05).There was a marked difference in 3-MH amounts in pectoralis major muscle and intercostal muscle between group B and C at 2 hr(P<0.05).The amounts of 3-MH in all muscles of rats in group B at 6 hr were increased significantly compared with these in group C(P<0.01).The gene expression of ubiquitin and C_2 subunit in all muscles of rats in group S increased significantly at 2 hr and 6 hr,as compared with rats in group B and C (P<0.01).And there were significant differences in gene expression of ubiquitin and C_2 subunit in all muscles between rats in group B at 2 hr,6 hr and those in group C(P<0.01).Conclusion The data suggested that the activity of ubiquitin system,one of important protein degradation pathways, and the proteolysis in respiratory muscle was continuously enhanced after burn injury,especially during burn sepsis.The findings implicate that further study of the degradation of protein in respiratory muscles and its relation with the respiratory function after severe burn injury and sepsis is indicated.