274 K. SCHREIER 
tion mechanism, a temporary hypoxia of the kidney may be partly responsible for 
the extreme hyperaminoaciduria in individual cases after birth. Furthermore the 
shortage of energy donors in the immediate postnatal period must be considered. 
It isremarkable indeed that the excretion of total amino-nitrogen and of single amino 
acids shows such a constancy during almost the entire life span. Only in very old 
people can one again find an increased excretion of some amino acids. At least in 
children a day-night rhythm of amino acid elimination has been detected. During 
the night the amino acid concentration in urine is higher. Since the urine volume is 
smaller the total amount is not elevated. The minimum of amino acid excretion 
occurs in the early morning hours. 
2. Nutrition 
a) Protein content 
It is not quite understandable why opinions differ as much as to whether the 
protein content of the food has an influence on amino acid elimination in the 
urine!’ 174, since it has been known for more than 50 years that some correlation 
exists (cf. PETERS AND VAN SLYKE!4"). Some authors!”®: 177 deny it almost entirely. The 
increase of amino-nitrogen elimination in the first days of life and the rise of the amino- 
nitrogen/total-nitrogen quotient from about 5—10%, clearly shows this influence. In later 
life, amino acid excretion during ingestion of a normal diet increases by about 
50-60%, in comparison with the fasting state®*. 176, After a high protein diet those 
amino acids which have a low 7;, value are excreted in higher amounts (histidine, 
threonine, lysine, tyrosine, etc., e.g. HUISMAN!84,186), A high protein diet has an unu- 
sually marked influence if administered to an organism deprived of proteins!”8. This 
we verified in severe cases of nutritional dystrophy of infancy. When these patients 
received an adequate amount of milk a very impressive hyperaminoaciduria resulted. 
It needs not to be emphasized that no direct relation exists between protein content 
of the food and amino acid excretion in urine, since several organs are inserted in the 
circuit. THURAU?"! has found that the urine of infants fed human milk (protein-poor) 
contained less amino acids than that of infants fed on cow’s milk formula. This has 
been confirmed by ScumiptT!”®; however, DusT1n!® did not observe great differences. 
In acute gastroenteritis in infancy a slight or very marked hyperaminoaciduria, 
parallel to the severity of the disease, can be found®®, 189, 181 (see also p. 268). In 
chronic nutritional disorders usually no significant change of the amino acid content 
of urine is detectable. In a few cases of celiac syndrome and mucoviscidosis a 
slight increase can be found: 182, CHoreEmts et al.183 found a hyperaminoaciduria in 
infants with “thirst-fever” which is difficult to interpret. 
b) Fluid 
The dependence of the amount of amino acid excretion on diuresis was discussed 
ardently a few years ago mainly in the German medical literature. In older children 
and in adults no dependence does exist!78; 179, 184, 185. Tt is maintained that under 
normal conditions, that is when the tubule function is intact, the adult kidney is 
able to reabsorb amino acids almost quantitatively, even under great variation of 
fluid intake. However, in young infants the rate of amino acid excretion increases 
more or less proportionately to the urine volume. 
References p. 279/283 
