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 severalfold. 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.