Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise

Am J Physiol. 1994 Dec;267(6 Pt 1):E1010-22. doi: 10.1152/ajpendo.1994.267.6.E1010.

Abstract

In this study, five men exercised the knee extensor muscles of one leg for 60 min (71 +/- 2% maximal work capacity) with and without (control) an oral supplement (77 mg/kg) of branched-chain amino acids (BCAA). BCAA supplementation resulted in a doubling (P < 0.05) of the arterial BCAA levels before exercise (339 +/- 15 vs. 822 +/- 86 microM). During the 60 min of exercise, the total release of BCAA was 68 +/- 93 vs. 816 +/- 198 mumol/kg (P < 0.05) for the BCAA and control trials, respectively. The intramuscular BCAA concentrations were higher (P < 0.05) for the BCAA trial and remained higher (P < 0.05) throughout exercise. In both trials, substantial quantities of NH3 were released, and when NH3 production equivalent to IMP accumulation was subtracted the net NH3 production was 1,112 +/- 279 and 1,670 +/- 245 mumol/kg (P < 0.05) for the control and BCAA trials, respectively. In contrast, the release of the essential amino acids (EAA) was much lower for the BCAA than the control trial (P < 0.05). When the BCAA were subtracted from the EAA (EAA-BCAA), the total release of EAA minus BCAA was lower (P < 0.05) for the BCAA (531 +/- 70 mumol/kg) than the control (924 +/- 148 mumol/kg) trial. These data suggest that BCAA supplementation results in significantly greater muscle NH3 production during exercise. Furthermore, the increased intramuscular and arterial BCAA levels before and during exercise result in a suppression of endogenous muscle protein breakdown during exercise.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Amino Acids, Branched-Chain / pharmacology*
  • Ammonia / metabolism*
  • Exercise*
  • Fatty Acids, Nonesterified / metabolism
  • Humans
  • Inosine Monophosphate / metabolism
  • Male
  • Muscles / metabolism
  • Oxygen Consumption
  • Proteins / metabolism*

Substances

  • Amino Acids, Branched-Chain
  • Fatty Acids, Nonesterified
  • Proteins
  • Inosine Monophosphate
  • Ammonia