Postsurgical muscle protein turnover in perfused hindquarters of the rat

Skeletal muscle protein synthesis and degradation were measured simultaneously in perfused hindquarters of adult female rats 0, 2, and 4 days after surgical trauma. In order to explore the role of decreased postoperative nutrient intake on muscle protein turnover, a group of rats were pair-fed to the level of food consumed by surgical traumatized animals. Protein synthesis was measured by the incorporation of 3H-L-phenylalanine into the myofibrillar (contractile) and sarcoplasmic (soluble) proteins of gastrocnemius muscle. Protein degradation rates were calculated from the release of myofibrillar 3-methyl histidine (3MH) during the perfusion. Surgical trauma significantly depressed myofibrillar and sarcoplasmic protein synthetic rates by 33 and 29%, respectively. Protein degradation, as assessed by 3MH release into perfusate, increased 25% on the second postoperative day but returned to control levels by the 4th day after surgery. Food restriction of the pair-fed control rats did not alter protein synthesis, however, protein degradation decreased significantly. In conclusion, the effect of trauma on protein turnover appears not to be due to decreased nutrient consumption.