[Effect of sepsis on the expression of ubiquitin and ubiquitinated protein in rat skeletal muscle].
OBJECTIVE
To study the regularity of ubiquitin and ubiquitinated protein expression in rat skeletal muscle during sepsis, and the molecular mechanism of enhancement in skeletal muscle protein catabolism.


METHODS
Wistar rats with sepsis were administered endotoxin peritoneally. The rats were randomly divided into 4 groups rats: 2, 6, 12 and 24 h after administration of endotoxin; each group (16) included normal controls. In vitro muscle incubation system with sufficient oxygen supply was used with amino acid automatic analyzer for detecting the proteolytic rate of the extensor digitorium longus(EDL) and soleus(SOL) muscle in the sample. The expression of ubiquitin and ubiquitinated protein in rat EDL muscle was determined by western blot.


RESULTS
Total proteolytic rate in the EDL muscle increased slightly at 2 and 6 h after administering endotoxin into the peritoneal cavity, and no significant difference at 12 and 24 h was observed. There was a progressive increase of 155% and 220% in myofibrillar proteolytic rate at 2 and 6 h, and 40% at 12 h, respectively, as compared with that of the normal controls. The expression of ubiquitin and ubiquitinated protein in the EDL muscle rose by 46% and 2.4 fold at 2 h and 6 h after administering endotoxin, while the ubiquitinated protein of high molecular weight was determined. No significant changes were noted in the expression of ubiquitin and ubiquitinated protein at 12 and 24 h.


CONCLUSIONS
The results indicate that activation of ubiquitin-proteasome pathway occurs in rat skeletal muscle during sepsis, and high expression of ubiquitin and ubiquitinated protein means that the substrate flowing into ubiquitin-proteasome pathway increases markedly, and then leads to muscle wasting.
Chai
J
J
Burns Institute, 304th Hospital, People's Liberation Army, Beijing 100037, China.
Wu
Y
Y
Sheng
Z
Z
D000818:Animals; D003546:Cysteine Endopeptidases / Q000502:physiology; D004731:Endotoxins / Q000633:toxicity; D008297:Male; D009097:Multienzyme Complexes / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D051381:Rats; D017208:Rats, Wistar; D018805:Sepsis / Q000378:metabolism*; D025801:Ubiquitin / Q000096:biosynthesis*
D004731:Endotoxins; D009097:Multienzyme Complexes; D009124:Muscle Proteins; D025801:Ubiquitin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex