272 K. SCHREIER 
the post-natal period probably results from the different stages of maturity of the 
transport mechanism in the tubuli of the kidney. Basically, the excretion of lysine is 
quickly reduced during the first month of life. It is also noteworthy that ethanol- 
amine is initially eliminated in the urine in large quantities, but about the third 
month of life, except in cases of severe liver damage and occasional cases of leukemia, 
its presence can no longer be demonstrated. O'BRIEN et al.4*! believe they have 
demonstrated methylglycine in early urines. 
By the 5th or 6th day of life the amino acid pattern has changed to the extent that 
the elimination of taurine, cystine and ethanolamine is decreased sharply. Proline 
and hydroxyproline have become quantitatively the principal amino acids. Young 
rats also excrete more hydroxyproline than adult animals!*?. The elimination of the 
majority of the other amino acid is more or less increased. This is especially true 
of glutamine’. Some urines even contain appreciable quantities of aromatic amino 
acids. The behavior of amino acids in urine after birth coincides in most respects with 




400 67 
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1d 3ds 5ds 7ds 10ds 14ds 21ds Gws Bws 3ms Gms Yms 12ms 
Fig. 3. a-Amino-nitrogen and non-protein nitrogen in mg/k/24-h and as amino-quotient (taken 
from Bickel: Physiolog. Entwicklung des Kindes). 
reactions of other processes related to protein metabolism, for example, with the 
activity curves of some coagulation factors!*. The extent to which the hyper- 
aminoaciduria of prematures and full-term infants is of renal origin can be definitely 
resolved by clearance studies. Table [V presents our values® from studies with 
infants and those of SERENI et al.2! compared to adult values!*.?8! (see also ref. 157). 
It is evident that an immaturity of the tubule function exists in infants. The relative 
hyperaminoaciduria of infants is sometimes even more marked than paper-chromato- 
graphic studies would suggest since the glomerular filtration rate in some prematures 
is severely decreased. 
In premature infants the hyperaminoaciduria is, in most cases, demonstrable for a 
longer period than in full-term infants. Furthermore, the excretion of the character- 
istic amino acids, proline and hydroxyproline, begins later. The essentials of prolin- 
uria and hydroxyprolinuria in infancy are not yet properly understood because the 
References p. 279/283 
