38 



Scientific Proceedings (51). 



27 (723) 



Distribution of amino acids in the body. 

 By Donald D. Van Slyke and Gustave M. Meyer. 



[From the Rockefeller Institute for Medical Research.] 

 In a recent paper (Journ. Biol. Chem., Sept., 1912) we have 

 shown by direct determinations (nitrous acid method) of the 

 amino acid nitrogen of the blood, that during the digestion of 

 protein amino acids pass from the alimentary canal into the blood. 

 The amino acid nitrogen reaches only a relatively low concentra- 

 tion in the blood (3-5 mg. per 100 c.c. after 24 hours fast, 10-12 

 mg. during digestion), because, as was found after intravenous 

 injection of alanine, the amino acids are either destroyed or 

 removed with great rapidity by the tissues. The object of the 

 present work was to obtain direct proof, by analysis of the tissues 

 themselves with the nitrous acid method, as to whether the amino 

 acids disappear from the blood as the result of destruction, of 

 synthesis to more complex compounds, or of mere concentration 

 in the tissues. The last explanation is the correct one. The 

 tissues (muscle, liver, kidney, spleen, pancreas) contain, stated 

 very roughly, about ten times the amount of amino acid nitrogen, 

 per 100 grams, that is found in the blood. The amount varies 

 in the different tissues, the brain being especially low, but about 

 the same order of magnitude in this respect appears to be normally 

 maintained among the different organs. Amino acids injected 

 into the blood, or absorbed during digestion, are immediately 

 taken up by the tissues; but the removal, although rapid, is never 

 complete, equilibrium being reached and maintained between 

 blood and tissues respectively. The means by which the amino 

 acids are held in the tissues appear to be physical rather than 

 chemical; for the acids can be extracted by even cold water or 

 dilute alcohol. The fact that the amino acids are many times 

 more concentrated in the tissues than in the blood excludes 

 osmosis as an explanation. The facts thus far known are con- 

 sistent with the assumption that the amino acids are taken up 

 from the blood and held in the tissues by adsorption, chemical 

 transformation of the adsorbed amino acids following later. This 

 transformation occurs much more rapidly in the liver than in the 

 muscles. 



