Abstract
Rates of whole body nitrogen flux (Q), protein synthesis (S), and breakdown (C), and skeletal muscle protein breakdown were measured in 24 growing premature infants. The infants were each studied twice. The first study (A) was conducted once the infants were clinically stable and ingesting an oral intake of at least 120 kcal/kg/d. The second study (B) was started 2 weeks later.
There was a marked increase in rates of skeletal muscle protein breakdown, from 0.93±0.21 g to 2.9±0.26 g/kg/d (p<0.01). During Study A, very low birth weight (<1500 g) infants had significantly higher rates than larger infants (1.19 cf 0.66 g/kg/d); however, these differences were no longer present during Study B; both groups showing a marked increase in muscle breakdown rates (2.95 cf 3.03 g/kg/d). There were no differences in Q, S or C with increasing postnatal age. It appears that skeletal muscle protein metabolism increases postnatally from about 8% to 24% of whole body protein turnover with a concommitant decrease in other tissues. Skeletal muscle has been estimated to constitute about 22% of total body protein in infants. Thus, these changes may reflect an increase in skeletal muscle protein turnover from a low rate to one that is in proportion to skeletal muscle's contribution to whole body protein.
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Pencharz, P., Masson, M., Desgranges, F. et al. 280 THE EFFECTS OF POSTNATAL AGE ON THE WHOLE BODY PROTEIN METABOLISM AND SKELETAL MUSCLE PROTEIN BREAKDOWN OF PREMATURE INFANTS. Pediatr Res 15 (Suppl 4), 486 (1981). https://doi.org/10.1203/00006450-198104001-00291
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DOI: https://doi.org/10.1203/00006450-198104001-00291