SIMULTANEOUS MEASUREMENTS OF FREE AMINO-ACID PATTERNS OF PLASMA, MUSCLE AND ERYTHROCYTES IN HEALTHY-HUMAN SUBJECTS

Muscle biopsy and blood samples were simultaneously collected from 27 healthy subjects for determination of free amino acid (AA) in plasma, muscle and erythrocytes (RBC) by reverse-phase high performance liquid chromatography and related their concentrations to deoxyribonucleic a cid (DNA), muscle alkali-soluble protein, s-albumin and s-total protei n. Extra- and intracellular water distribution in muscle was estimated with a modified chloride method. The majority of the AA showed higher concentration in intracellular water (ICW) than in plasma; exceptions were the concentrations of branched-chain amino acids (BCAA), phenyla lanine and tyrosine exhibiting muscle/plasma and RBC/plasma ratios of 1.0-1.4. Muscle arginine and lysine as well as RBC citrulline showed h igher concentrations in younger female subjects when compared to males whereas in the three compartments all other AA were present in higher concentrations in the males than in the female subjects. The levels o f valine and asparagine in muscle as well as serine, ornithine, methio nine and BCAA in RBC were higher in the younger than in the elderly su bjects, On the other hand, muscle arginine and plasma histidine levels were higher in the elderly than in the younger subjects. There were s ignificant positive correlations between plasma, muscle and RBC AA con centrations for a large number of AA, specially BCAA, The RBC BCAA con centrations correlated most strongly with the ratio of alkali-soluble protein to DNA in skeletal muscle (P < 0.002) and were also significan tly correlated to serum albumin and total proteins. The results presen ted here are proposed to be used as reference data for simultaneously comparing the AA profile in muscle, plasma and RBC in various disease conditions.