TIME STUDIES ON FREE AMINO ACID LEVELS OF VENOUS PLASMA DURING THE NEONATAL PERIOD

A simplified method of ion-exchange chromatography of essential amino acids on small amounts of human plasma is described. The precision of the instrument and the reproducibility was to be compared with those achieved with automatic amino acid analyzers. The method has been applied in a survey of venous plasma free amino acid levels and urinary concentrations during the neonatal period. A considerable general decrease of the free amino acid levels was seen already during the first postnatal day. This was most marked in the branch-chained amino acids, where levels that were low for infants were seen already after the first hours of starvation. The well known high urinary excretion of amino acid nitrogen was found to be due to a high excretion of a limited number of amino acids.