Changes of protein degradation in skeletal muscle of patients with severe burn sepsis and its biological mechanism. Blood, 24-hour urine and quadriceps femoris samples were collected from 9 patients with severe burn sepsis and 9 patients with plastic surgery at the same time (control group). The contents of cortisol and TNF-α in blood were determined by radioimmunoassay, and the excretion of 3- methylhistidine in urine for 24 hours was determined by HPLC. The changes of gene expression and protein expression in quadriceps femoris were detected by RNA blotting and immunohistochemistry respectively. The results showed that the concentrations of cortisol and TNF-α in peripheral blood of burn sepsis group were significantly higher than those of control group (P