IS THE METABOLIC RESPONSE TO SEPSIS IN SKELETAL-MUSCLE DIFFERENT IN INFANTS AND ADULTS - AN EXPERIMENTAL-STUDY IN RATS

In this study we compared the effect of sepsis on muscle protein metabolism in infant (3 to 4 weeks) and adult (3 to 4 months) rats. Sepsis was induced by cecal ligation and puncture (CLP). Control animals underwent sham operation. Sixteen hours after CLP or sham operation, metabolic studies were performed in incubated intact extensor digitorum longus muscles from infant rats or in strips of the same muscle from adult rats. Protein synthesis rate was determined as incorporation of 3H-phenylalanine into protein; total and myofibrillar protein breakdown rates were determined as release of tyrosine and 3-methylhistidine, respectively. Mortality rate following CLP was similar in both age groups. Basal protein synthesis rate was 3 times higher, total protein breakdown rate was 50% higher, and myofibrillar protein breakdown rate was 3 times higher in infant than in adult animals. However, the relative changes in protein turnover rates induced by sepsis were similar in infant and adult rats: protein synthesis rate decreased by approximately 30%, total protein breakdown increased by 40% to 50%, and myofibrillar protein breakdown increased several-fold. The data suggest that despite prominent differences in basal protein turnover rates between infant and adult rats, the effect of sepsis on muscle protein metabolism is not age dependent. © 1992.