The Distribution Of Amino Acids 

 Between Cellular And Extracellular Fluids 



Relation To Growth 



HALVOR N. CHRISTENSEN, Ph. D. 



Director, Department of Research Chemistry, Children's Hospital 



One of the most significant reactions of living matter we 

 can write, light-heartedly, in this way: 



1 

 amino acids ~ *" proteins 

 2 



The balance between reactions 1 and 2 determines whether 

 growth or wasting occurs. All factors that accelerate growth 

 or that accelerate catabolism must affect this balance, possibly 

 by direct effects upon these reactions. 



Our approach to the problem has been to break down this 

 reaction into two stages, like this: 



3 



extracellular — 



amino acids ■*- 



4 



cellular 1 



amino acids T~* proteins 



5 to 40 x as 2 

 concentrated 

 cell boundary 



Van Slyke and Meyer pointed out in 1913 that the free amino 

 acids of tissues are at much higher concentration than those 

 of the plasma, and that amino acids enter the tissues against 

 these concentration gradients. The necessary implication of 

 this finding is that each amino acid molecule is brought into 

 the cell by an active, energy-requiring process, undoubtedly 

 enzymatic. Could this be a site of control of protein synthesis 

 and hence of growth? Might testosterone, for example, in- 

 crease the degree to which muscle cells concentrate amino 

 acids ? 



First, we have analyzed plasma and tissues to determine if 

 (Bulletin of the New England Medical Center X: 108-111, June, 1948) 



II 4 



