AMINO ACIDS IN PRE- AND POST-NATAL PERIODS 269 
acids in the post-prandial period is mainly influenced by the rate of breakdown of 
ingested proteins, the quantity of amino acids released and the rate of absorption of 
each individual amino acid®. This resorption rate is, of course, influenced by the 
concentration of amino acids in the chyme and by the presence of saccharides and 
perhaps of fats. In our studies the blood levels of lysine, tryptophane, isoleucine and 
valine showed a distinctive increase after ingestion of meat or casein. These results 
agree quite favorably with those obtained by FRAME*? in his examination of adults. 
On the other hand, we should note that several amino acids decrease after a protein 
load; for instance alanine and glycine”. Apparently their use in protein synthesis is 
greater than the supply. The ingestion of individual amino acids®*~*? leads to ap- 
preciably higher peaks®* than the same quantity of amino acid supplied as protein or 
in protein hydrolyzates. 
According to JACCOTTET ef al.°° in prematures the maximum of amino-nitrogen 
after oral ingestion of hydrolyzates is reached earlier than in full-term babies. Low- 
value-proteinhydrolyzates change the amino acid levels in the sense of a temporary 
imbalance. 
The ingestion of monosaccharides decreases the amino-nitrogen content of the 
plasma, 102, 240. The decline in the blood levels of the individual amino acids 
varies!3 and is especially impressive with isoleucine’®’. ALBANESE ef al.® claim to 
have observed a decrease in tryptophane elimination in urine following a glucose load, 
while the other amino acids remained unchanged. This is in contradiction to the 
experimental results of BUTLER AND SARETT!4 who reported that tryptophane excre- 
tion is more or less independent of the carbohydrate content of food. MUNRO AND 
THomson?® also have been unable to detect an influence of monosaccharides on 
tryptophane elimination. Fat has no certain influence on the levels of most amino 
acids. 
Instarvation or in the so-called absolute protein-minimum stage the amino-nitrogen 
content and the levels of the amino acids decrease until only shortly ante exitum. 
At this time the levels increase above the physiological range. STELGENS AND BOTHE! 
have found in two infants on a long standing protein-free diet that a relative rise in 
amino acid values in urine occurs. Animal experiments have shown, that the content 
of free amino acids in the liver is increased during starvation!°*. Our studies with 
M4C-labeled lysine in young rats confirm these findings and revealed that the in- 
corporation rate of [Cjlysine in protein shortage is increased in the visceral organs, 
especially in the liver, while the incorporation into other structures, for instance, the 
erythrocytes, is sharply decreased. From this one may conclude that in extreme 
protein deficiency there is a shunting of protein metabolism to the benefit of essential 
synthetic processes in the liver, kidneys, etc. This effect is so pronounced, that in 
newborn rabbits, even shortly before death, labeled lysine is incorporated at a high 
rate into liver proteins. 
We do not believe that the hypoaminoacidemia observed in severe nutritional 
dystrophy (kwashiorkor etc.) is due to enzyme inactivity but rather that it results 
from an increased utilization of amino acids for energy-yielding processes and 
partly through a higher uptake by the liver. 
The kidney has only an insignificant influence on the amino acid content of the 
blood. Even in the final stages of nephrosclerosis, we could like many other authors, 
find no significant changes in most amino acids. Only alanine and glycine were 
References p. 279/283 
