VOL. 4 (1950) 



BODY SIZE AND TISSUE RESPIRATION 



251 



surface and the centre of the sUce. Hence a concentration gradient and a rate of diffusion 

 which might be sufficient to saturate the cells in vivo may become a limiting factor 

 in vitro. 



Both difficulties — rapid exhaustion and slow diffusion — can be overcome by 

 increasing the concentration of the 'relevant' metabolites in the medium. This con- 

 sideration raises the question of what are 'relevant' substrates. Among the very large 

 number of organic substances known to occur in plasma and serum (listed in Table I) 

 only a few have been found to influence the oxygen uptake in vitro. They are glucose, 

 lactate, pyruvate, the acids of the tricarboxylic cycle, and glutamate (or glutamine),and 

 some closely related substances such as phosphorylated intermediates of glycolysis 

 which need not be considered separately. A few special amino acids {e.g., tyrosine, 

 phenylalanine, proline) can increase the respiration of liver, kidney, and sperma- 

 tozoa^^' ®^' ®^' ^*, but although these effects may be of importance in relation to the 



TABLE I 



COMPOSITION OF HUMAN BLOOD PLASMA 



Substance 



mg/ioo ml 



Average or 



representative 



value 



Range or 

 standard 

 deviation 



References 



Nitrogenous substances 



Protein (total) 

 Albumin 

 ai-Globulin 

 Qg -Globulin 

 ^-Globulin 

 y-GlobuIin 

 Fibrinogen 

 Non-protein nitrogen (total) 



Amino-N (as N, ninhydrin method) 

 Amino-N (as N, nitrous acid method) 



Alanine 



Arginine 



Citrulline 



Glutamic acid 



Glutamine 



Glycine 



Histidine 



Iso-leucine 



Leucine 



Lysine 



Methionine 



Phenylalanine 



Threonine 



Tryptophane 



Tyrosine 



Valine 

 Ammonia (as N, whole blood) 

 Creatine 

 Creatinine 

 Glycocyamine 

 Urea (as N) 

 Uric acid 

 Allantoin 

 Allantoin (dog) 



References p. 26y-26g. 



below 



6720 

 4040 

 310 

 480 

 810 

 740 

 340 

 25 

 4.1 

 4.4 

 3-97 

 2-34 

 0.50 



3-41 

 5-78 

 1.77 

 1.42 

 1.60 

 1.91 



2.95 

 0.85 



1.38 

 2.02 

 1.08 

 1.48 

 2.83 

 0.05 

 0.9 

 0.4 

 0.26 

 12 

 4 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 

 18- 

 3-4- 

 3-7- 



S.D. 



S.D. 



0.38- 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 



0.46- 



S.D. 



S.D. 



S.D. 



S.D. 



S.D. 



270 

 51 

 83 



126 



151 

 59 

 30 

 5-5 

 5-9 

 0.70 

 0.62 

 0.59 

 1-39 

 1-55 

 0.26 

 o.i8 

 0.31 



0.34 

 0.42 

 1.48 

 0.32 



6.45 

 0.21 



0.37 

 0.34 



0.62-1.02 



0.28-0.62 



0.24-0.28 



10-17 



2-6 



0.3-0.6 



1. 1-3.0 



