Erythrocytes participate significantly in blood transport of amino acids during the post absorptive state in normal humans.

To investigate the participation of erythrocytes in the blood transport of amino acids during the course of intestinal absorption in humans, erythrocyte and plasma amino-acid concentrations were determined following ingestion of an oral load of amino acids. In addition to baseline plasma and erythrocyte amino acid concentrations in 18 subjects, plasma and erythrocyte amino acids kinetics during the 125 min following an oral amino acid load were further determined in 9 of the 18 subjects. The results showed that human erythrocytes contained most amino acids at similar or higher concentrations than plasma. Furthermore, the correlations observed between plasma and erythrocyte contents clearly indicated that erythrocytes were involved in the transport of amino acids by the blood. For some amino acids erythrocyte transport sometimes exceeded that of plasma. Significant correlation coefficients showed that strong plasma-erythrocyte relationships existed for alanine, valine, methionine, isoleucine, leucine, phenylalanine, and ornithine. In conclusion, our data supported the hypothesis that both blood compartments, plasma and erythrocytes, are involved significantly in the blood transport of amino acids in humans during the postabsorptive state.