OCCURRENCE OF FREE AMINO ACIDS — VERTEBRATES 263 
THE BEHAVIOR OF AMINO ACIDS IN BODY FLUIDS DURING 
DEVELOPMENT AND GROWTH: PHYSIOLOGY AND PATHOLOGY 
Ke SCHREIBER: 
Children’s Hospital, University of Heidelberg, Heidelberg (Germany) 
Prior to the development of reliable methods for the determination of single amino 
acids, German pediatricians had found that the amino-nitrogen content in the urine 
of the newborn and especially of prematures is definitely higher than that found 
during later life. For several decades this finding has evoked a discussion as to 
whether the increased amino acid loss is of renal origin or whether it is due to the 
TABLE 
THE MATURITY OF NEWBORNS AND THE LEVELS OF DIFFERENT PROTEIN METABOLITES 
IN BLOOD ACCORDING TO LICHTENSTEIN 
Averages value in mg/10o ml 


Birth weight Non-protein N Urea-N Creatinine AOI Uric acid 
nitrogen 
500-1000 g 27.44 Ti O7 5.05 9.06 2.40 
IOOO—1500 g 30.27 13.42 5.19 8.31 3e02 
1500-2000 g 33.03 13572 4.90 8.02 3°25 
2000—2500 g 33-55 14.01 4.86 SRE, 3.605 
2500-3000 g 32.41 13.86 4.33 Wee 3-55 
3000 g and above 35-05 14.93 4.71 6.48 3.70 


immaturity of the liver metabolism. We are now in a position to present a more or 
less clear picture of the behavior and the metabolic processes of the amino acids in 
the pre- and post-natal periods in health and disease. 
A. BLOOD 
RABINOWITSCH! and 5 years later Morse? and VAN SLYKE AND MEYER? were ap- 
parently the first to ascertain an increased amino-nitrogen content in the blood of 
the umbilical cord. This finding has been confirmed by several workers (cf. refs. 4-15). 
The most profound study was done by LICHTENSTEIN!®. He showed clearly that the 
amino-nitrogen content depends on the maturity of the newborn as Table I demon- 
strates. According to POMMERENKE", the amino-nitrogen level, like that of the other 
non-protein-nitrogen substances, is slightly higher in the cord arteries than in 
the cord vein. The results of this early research period have recently been ex- 
tended through the use of contemporary methods (see for example, the studies of 
References p. 279/283 
