The influence of endurance training and an acute bout of exercise on plasma concentrations of free amino acids and the intermediates of branched-chain amino acid (BCAA) metabolism were investigated in the rat. Training did not affect the plasma amino acid levels in the resting state. Plasma concentrations of alanine (Ala), aspartic acid (Asp), asparagine (Asn), arginine (Arg), histindine (His), isoleucine (Ile), leucine (Leu), lysine (Lys), methionine (Met), phenylalanine (Phe), proline (Pro), serine (Ser), threonine (Thr), and valine (Val) were significantly lower, whereas glutamate (Glu), glycine (Gly), ornithine (Orn), tryptophan (Trp), tyrosine (Tyr), creatinine, urea, and ammonia levels were unchanged, after one hour of treadmill running in the trained rats. Plasma concentration of glutamine (Glu), the branched-chain keto acids (BCKA) and short-chain acyl carnitines were elevated with exercise. Ratios of plasma BCAA BCKA were dramatically lowered by exercise in the trained rats. A decrease in plasma-free carnitine levels was also observed. These data suggest that amino acid metabolism is enhanced by exercise even in the trained state. BCAA may only be partially metabolized within muscle and some of their carbon skeletons are released into the circulation in forms of BCKA and short-chain acyl carnitines.
Bibliographical noteFunding Information:
From the Institute for Enzyme Research, Biodynamics Laboratory and Department of Biochemistry, University of Wisconsin, Madison. Supported in part by the NIH Grant No. AM 10334. the Vilas Trust, and the Biodynamics Laboratory of the University of Wisconsin at Madison. Presented in part at the 1985 Meetings of the Federation of the American Society for Experimental Biology at Anaheim, CA [Fed Proc 44:?64. I985 (abstr 2062)j. Address reprint requests to F.W. Stratman. PhD, Institute for Enzyme Research, 1710 University Ave. Madison, WI 53705. Q I987 by Grune & Stratton, Inc. 0026-0495/s7/3608-0008$03.00/0