Dynamic Change of Serum Levels of Some Branched-Chain Amino Acids and Tryptophan in Athletic Horses After Different Physical Exercises

Physical exercise induces several adaptations involving modulation of the energetic pathways to meet the energy demand during physical exercise. The branched-chain amino acids, leucine in particular, are considered as the most relevant amino acids, especially for exercise physiology. In this study, the change of leucine, valine, and tryptophan concentration was investigated in athletic horses before and after different exercise type. A total of 40 sport horses were equally divided into 4 groups according to the exercise type: group A (jumping), group B (reining), group C (32 km ride), and group D (72 km ride). Blood samples were collected before (TPRE), immediately after (TPOST), and 30 minutes after (TPOST30) the race to assess leucine, valine, and tryptophan concentration. Two-way analysis of variance showed an effect of time and/or exercise on the serum leucine, valine, and tryptophan values in all groups (P < .01). Lower leucine and valine values were found in groups A, B, and D at TPOST and TPOST30 respect to TPRE, whereas group C showed higher values at TPOST and TPOST30 compared with the values found at TPRE. All groups showed increased tryptophan values at TPOST and TPOST30 compared with TPRE. Lower leucine, valine, and tryptophan values were found in group D at TPOST30 compared with the values found at TPOST. These dynamic changes suggest the involvement of amino acid metabolism during different exercise types. These findings are probably related to the complex physiological adaptations to exercise stressor that allow reestablishment of the homeostatic equilibrium of the organism.