FREE AMINO ACIDS OF BLOOD AND URINE 229 
cycles in a given individual, whose amino acid excretion has been repeatedly in- 
vestigated at various intervals during a period extending through 6 consecutive years. 
There was found regularly that a maximum histidine output, of highly reproducibl 
magnitude, occurs at a time when there was maximum estrogenic activity sae 
the course of menstrual cycles, namely around mid-cycle. Observations made at 
6-years interval in the same individual were perfectly superposable as regard to 
lower and higher urinary histidine output during the cycles, and also as regard to 
the occurrence of the maximum output at mid-cycle. These observations have been 
cross-checked by use of two different ion-exchange chromatographic methods and 
a specific enzymatic decarboxylation method for histidine determination®®. 
2) Normal pregnancy. This physiological circumstance has been extensively 
investigated by SoupartT® during the past 6 years. Normal pregnancy is characterized 
by a generalized hyperaminoaciduria, affecting essentially the following amino 
acids listed in decreasing order of hyperexcretion during pregnancy: histidine, 
glycine, threonine, serine, alanine, tyrosine, phenylalanine, isoleucine and arginine. 
Unfortunately, although very typical of pregnancy in an individual whose usual 
amino acid excretion is well known, this hyperaminoaciduria, which appears very 
early after fecondation has occurred, cannot be used as a diagnostic test for pregnancy 
because of the very large variations of normal] excretion levels among different 
individuals. This has been demonstrated beyond any doubt by Soupart®. The 
mechanism of this phenomenon will be dealt with in one of the following sections. 
3) Effects of some hormonal factors. In experiments designed to assess an inter- 
pretation of the hyperaminoaciduria occurring during normal pregnancy, SOUPART® 
has investigated the effects on amino acid excretion of large doses of estrogens (estra- 
diol benzoate) and of dihydrocortisone administered to patients suffering of prostate 
carcinoma. In those instances, and specially after dihydrocortisone, a hyperamino- 
aciduria of the type observed in pregnancy has been induced in the patient, who 
was formerly normal in this respect. Adrenal hormones are known to increase def- 
initely the glomerular filtration rate and this may be responsible for the hyper- 
aminoaciduria observed in the patient as well as that observed in the course of 
pregnancy, since this latter state is known to comprise hyper-hormonal activities. 
4) Effects of high protein diet. It seems that free amino acid excretion is not, or 
rather poorly influenced by overdosage of protein in the diet. Even a very large 
supply of 3-4 g of protein/kg of body weight does not seem to affect significantly 
the free-amino acid urinary outputs. But, as already stated, there is an exception, 
namely in the case of 1-methylhistidine, the excretion of which is correlated not 
to the total protein supply but to that part of the supply which consists of meat. 
Normal aminoaciduria in healthy children 
Normal newborns show a higher total aminoaciduria, when related to total ni- 
trogen output, than do normal healthy adults. This phenomenon is even more pro- 
nounced in premature babies. Such a situation might be the result of less complete 
reabsorption of free amino acids by immature renal tubular mechanisms. The 
relative amount of a-amino nitrogen excreted in urine is 1°% of total nitrogen in 
adults, approx. 3° in newborns and more than 4% in premature babies”? 4) ?°. 
This situation is normalized during the first year of life, but until the age of 2 years, 
References p. 261/262 
