350 OCCURRENCE OF FREE AMINO ACIDS — VERTEBRATES 
FREE AMINO ACIDS IN THE BLOOD OF MAN AND ANIMALS 
I. METHOD OF STUDY AND THE EFFECTS OF VENIPUNCTURE 
AND FOOD INTAKE ON BLOOD FREE AMINO ACIDS 
GEORGE ROUSER, BOHDAN JELINEK, ARTHUR J. SAMUELS 
AND KEIJI KINUGASA* 
Departments of Biochemistry and Medicine, City of Hope Medical Center, 
Duarte, Calif. (U.S.A.) 
Our interest in the free or easily extractable amino acids and related ninhydrin positive 
substances of cells and body fluids stems to a great extent from the fact that free 
amino acids appear to be precursors of protein while preformed proteins or peptides 
are either of minor importance or not involved in protein synthesis. The free amino 
acid pool and the regulatory mechanisms involved in its maintenance thus bear an 
important relationship to cell growth and reproduction. The relationships might be 
altered in pathological states, such as leukemia, in which there is a disturbance of 
growth. The possibility that the metabolism of individual amino acids might be 
different in the leukemias and that differences might be utilized in controlling these 
conditions constituted another reason for the present studies. The influence of cyto- 
toxic drugs on amino acid metabolism has been studied in an effort to define, at least 
in part, the mode of action of the drugs. Elucidation of changes produced by drugs 
may be useful in the development of new measures for the control of the leukemic 
process. 
These investigations are extensions of previous studies!~*. The objectives were: 
(1) To determine the nature of the constituents in the free amino acid pools of plasma 
and cells; (2) to define relationships existing between plasma and cellular free amino 
acids; (3) to detect deviations from normal in the leukemias; and (4) to determine 
the effects on free amino acid levels of cytotoxic drugs commonly administered to 
patients with leukemia. 
A number of earlier reports on blood amino acid nitrogen in various pathological 
states involving the hematopoietic system were available when we began our studies. 
GREENE AND Connor‘ and Luck? had reported that amino acid nitrogen was elevated 
in polycythemia, and ScHmripT® reported that the amino acid nitrogen content of the 
blood was frequently moderately increased in leukemia. OKADA AND HayAsuHI’ had 
also found a moderate increase of amino acid nitrogen in leukemia, particularly of 
the myelogenous type. 
BEATON et al.8 reported an elevation of plasma glutamic acid levels in malignancy. 
They noted that total amino nitrogen in the blood, as determined by a modification 
of the Folin method, was not significantly elevated above normal. Subsequently, 
WHITE ef al.®:}° observed an increase in the plasma glutamic acid level in other 
conditions and showed that there was a rise in the free glutamic acid concentration 
* Present address: Professor OKINAKA’s Clinic School of Medicine, University of Tokyo, 
(Japan). 
References p. 447/448 
