449 
INVITED DISCUSSION 
FREE AMINO ACIDS IN PLASMA, 
BRAIN AND MUSCLE FOLLOWING HEPATECTOMY 
EUNICE V. FLOCK, anp JESSE L. BOLLMAN 
Mayo Clinic and Mayo Foundation, Rochester, Minn. (U.S.A.) 
In 1924 BoLLMAN, MANN AND MAGATH! demonstrated the importance of the liver 
in the maintenance of normal jlevels of free amino acids in blood and tissues. 
The formation of measurable amounts of urea ceased after removal of the liver 
from the dog. Increases in the concentration of free amino acids in blood, urine, 
and muscles? were found in the dehepatized dog, which were approximately equal 
to the amount required for urea that would have been formed by the normal ani- 
mal. 
When the free amino acids in the plasma of the dehepatized dog were examined 
by paper-chromatographic technics, increased levels of 15 amino acids or derivatives 
were found®. In muscle, in addition to small increases observed in the content of 
other amino acids, an increased concentration of glutamine was found associated 
with a decreased concentration of glutamic acid?. In brain tissue, however, a 5-fold 
increase in the amount of glutamine occurred without a corresponding decrease in 
glutamic acid, and smaller increases in the amounts of other amino acids such as 
phenylalanine and tyrosine were also found. 
Intravenous administration of large amounts of glucose suppressed the accumula- 
tion of the free amino acids in plasma® and muscle® of the dehepatized dog so that 
normal levels could be maintained. Because administration of glucose did not prevent 
increases of the amino acids in plasma and muscles of the dehepatized-depan- 
creatized dog, but glucose with insulin did, it was concluded that the effect of glucose 
on the level of free amino acids in the dehepatized dog was produced by stimulation 
of the secretion of insulin. It appeared that insulin would promote the synthesis 
of protein from free amino acids in plasma and muscles of the dehepatized dog. 
In the depancreatized dog with a liver, high levels of amino acids were not found 
in plasma or tissues due to formation of urea by the liver. Thus, this insulin effect 
on the levels of amino acids in plasma and tissues was most clearly seen in the de- 
hepatized dog. 
Curiously, the administration of glucose with or without insulin had no effect on 
the progressive increase in glutamine and other amino acids which occurred in the 
brain of the dog, after removal of the liver. The effect of the absence of the liver on 
the levels of free amino acids is, therefore, more clearly seen in the brain than in 
other tissues. These increases in content of free amino acids in the brain are of particu- 
lar interest because liverless dogs under the most favorable conditions survive 
about 2 days and then die in hepatic coma. 
Increases in the content of total amino acids in the brains of dogs with Eck’s 
References p. 460 
