Human erythrocyte and plasma amino acid concentrations during exercise

Purpose: This investigation examined the effects of exercise and maltodextr in (Md) or placebo (Pl) ingestion on plasma and erythrocyte concentrations of amino acids. Methods: The erythrocyte and plasma concentrations of 17 am ino acids, as well ay plasma glucose and insulin, were analyzed in eight he althy trained male subjects before, during, and 25 min after 90-min cycle e rgometer exercise at 65% peak oxygen uptake. The two treatments involved in gestion of orange-flavored water (Pl) or orange-flavored 10% maltodextrin s olution (Md. Results: Two-way ANOVA revealed 1) that plasma concentrations of alanine and tyrosine changed significantly during the treatments, 2) tha t the plasma concentrations were significantly different between treatments for glycine and threonine, 3) that all erythrocyte concentrations increase d significantly throughout the treatments except for arginine and tyrosine, and 4) that there were no significant differences in erythrocyte concentra tions between the treatments. Three-way ANOVA highlighted the significant d ifferences in the time responses between plasma and erythrocyte concentrati ons; the changes in erythrocyte levels from rest bring significantly differ ent from plasma for all amino acids except aspartic acid, glycine, and orni thine. Plasma glucose concentrations became elevated and remained above res t values in Md but fell below rest values in Pl; the differences in concent ration between treatments were significant. Correspondingly, plasma insulin was significantly higher in Md during exercise. Conclusion: These results highlight that far from being slow in the uptake of amino acids, the erythr ocyte in fact sequesters amino acids at an appreciable rate during exercise without a corresponding elevation in the plasma amino acids. For a greater understanding of amino acid changes during exercise, the analysis of both plasma and erythrocytes is recommended.