[Determination by 15N tracer kinetics of the half-life of total body protein in premature and mature infants].

Based on 15N-tracer techniques important data of the intermediary protein metabolism can be assessed by compartment analysis. We calculated the half-life of whole body proteins in five preterm and five full term infants in addition to commonly used parameters of the protein metabolism e.g. protein synthesis rate, protein breakdown rate, N-turnover rate, size of metabolic pool, half-life and reutilization of aminoacid-N and the rate of endogenous urinary-N. The infants were aged 27 +/- 4 and 31 +/- 13 days resp. The half-life of whole body proteins were found to be 7.5 +/- 1.8 days in the premature infants and thus significantly shorter than the 16.0 +/- 3.8 days for the full term infants. The differences in the half-life of protein as well as protein synthesis rate and protein breakdown rate reflect the rapid proteinturnover in premature infants in comparison to full term infants.