Plasma Amino Acids After Birth

The concentration of the free amino acids of plasma during the neonatal period were studied by ion-exchange column chromatography in infants born prematurely or at term. In prematures the effects of 4% protein formula were compared with 2% protein formula. The changes in concentration at 1, 2, 3, and 4 hours postprandial were also studied in two prematures aged 10 and 25 days. A wide range for most amino acids especially in the premature group was observed. Increased concentrations of tyrosine up to 26 mg/100 ml as late as the fiftyseventh day of life were noted. A steady postnatal decrease for lysine, taurine, and threonine was found in the few days of life from the high cord blood concentrations toward the base-line values of infancy.