CHANGES OF FREE AMINO-ACIDS IN PLASMA OF HEALTHY SUBJECTS INDUCED BY PHYSICAL EXERCISE

In 8 healthy men a 20-min load of 1.5 W/kg body wt on a bicycle ergometer led to a significant increase of alanine and decline of leucine. Exhausting exercise caused a highly significant increase of alanine and a decline of isoleucine, threonine, ornithine, leucine, serine, glycine, asparagine and glutamine. The methionine and citrulline level also declined. The total amino acids did not change. Physical exercise led to a marked increase of serum ammonia and uric acid. Urea N changed little and had a declining tendency. The rise of alanine suggests the existence of a glucose-alanine cycle; the drop of ornithine and citrulline is most probably associated with the inhibition of ureogenesis in the liver. The reduction of leucine and isoleucine is probably the result of the entry of these amino acids into muscle and their deamination.