Effects of a competitive triathlon on plasma concentrations of tryptophan and branched-chain amino acids

Resumo

The aim of this work was to determine the acute responses of tryptophan and branched chain amino acids to a triathlon competition. Fourteen male triathletes were studied. All took part in a international triathlon race consisting of 1,5 km swimming, 40 km biking and 10 km running. Venous blood samples were drawn before (-24 h) and after (15 min) the triathlon. Plasma concentration of branched chain amino acids and total and free tryptophan were determined. Branched chain amino acids decreased from 463 - 108.3 to 364 - 98.9 mol/L (p < 0.03). Free tryptophan increases from 9.2 to 16.3 mol/L (p < 0.006). Furthermore the ratio of free trytophan to branched chain amino acids increased from 2.07 - 0.48 to 4.24 - 0.79 (p < 0.001). This increases the rate of transport of tryptophan accross the blood-brain barrier and also increases the rate of synthesis of 5-hydroxytryptamine in the central nervous system. A high presence of 5-hydroxytryptamine in the brain develops physical and mental fatigue during the triathlon. This data support the participation of amino acids in fatigue process during triathlon