FREE AMINO ACIDS OF BLOOD AND URINE DBT 
the precision of the determination is of the order of + 5% when the manual pro- 
cedure is used. For amino acids whose 24-h outputs average 10 mg, the relative 
error may rise to 10% or more. When determinations are made by use of the 
automatic procedure the precision which can be attained is of the order of 2 or 
3%, even for amino acids which have low urinary outputs. 
Other amino acids are regularly present in urine but in very minute amounts, 
lower than 10 mg/day. Still others are occasionally present but in non-measurable 
amounts or traces. 
Quantitative data for 23 amino acids in a group of 15 normal healthy adults, 
six males and nine females, are shown in Table I, drawn from a paper by SOUPART?®. 
Fig. 2 shows, on a molar basis, that nine of these amino acids, listed in decreasing 
order of average excretion, add up to approx. 85° of the total amino acid excretion. 
In this group, approximate values are given only for glutamine which corresponds 
to an excretion of at least 300 wmoles or approx. 50 mg/day. The remaining 14 
amino acids form only 15% of the total excretion. Differences in the average figures 
of the latter are therefore not to be taken as significant. On a normal protein diet, 
for instance, a supply of protein varying between 70 and 125 g/day, total urinary 
nitrogen may vary from g to 18 g/24h, of which approx. 3% in the average is 
TABLET 
DAILY URINARY OUTPUT OF 23 FREE AMINO ACIDS IN 15 NORMAL ADULT SUBJECTS 
Nine women and six men. Values expressed in symoles/24 h (SOUPART?®). 

A. g amino acids (85-90%, of total) 

Range Average 
Glycine 710—4160 1687 
Taurine 220-1850 812 
Histidine 130-1370 790 
1-Methylhistidine 130— 930 433 
Glutamine* At least 350 
Serine 310— 620 374 
3-Methylhistidine 180— 520 323 
Alanine 60— 500 257 
fp-Aminoisobutyric acid O— 500 252 
Total At least 5278 «moles 
B. 14 amino acids**, excreted in small amounts (0-300 yemoles) in the average 65 yumoles 
65 xX 14 = 910 wmoles 
Total A+B Approx. 6200 zmoles 
A = at least 85° of total aminoaciduria. 
B = no more than 15% of total aminoaciduria. 

* Minimal values (see p. 222); glutamic acid added to glutamine on a molar basis since freshly 
voided urine does not contain glutamic acid. 
** In decreasing order of average daily output: threonine, tyrosine, phenylalanine, isoleucine, 
leucine, cystine 1/,, lysine, valine, f-alanine, aspartic acid, methionine, a-aminoadipic acid, 
arginine and ornithine. 
References p. 261/262 
