Postexercise net protein synthesis in human muscle from orally administered amino acids.
We examined the response of net muscle protein synthesis to ingestion of amino acids after a bout of resistance exercise. A primed, constant infusion of L-[ring-2H5]phenylalanine was used to measure net muscle protein balance in three male and three female volunteers on three occasions. Subjects consumed in random order 1 liter of 1) a mixed amino acid (40 g) solution (MAA), 2) an essential amino acid (40 g) solution (EAA), and 3) a placebo solution (PLA). Arterial amino acid concentrations increased approximately 150-640% above baseline during ingestion of MAA and EAA. Net muscle protein balance was significantly increased from negative during PLA ingestion (-50 +/- 23 nmol. min-1. 100 ml leg volume-1) to positive during MAA ingestion (17 +/- 13 nmol. min-1. 100 ml leg volume-1) and EAA (29 +/- 14 nmol. min-1. 100 ml leg volume-1; P < 0.05). Because net balance was similar for MAA and EAA, it does not appear necessary to include nonessential amino acids in a formulation designed to elicit an anabolic response from muscle after exercise. We concluded that ingestion of oral essential amino acids results in a change from net muscle protein degradation to net muscle protein synthesis after heavy resistance exercise in humans similar to that seen when the amino acids were infused.
Tipton
K D
KD
Metabolism Unit, Shriners Burns Institute, and Departments of Surgery and Anesthesiology, University of Texas Medical Branch, Galveston, Texas 77550, USA.
Ferrando
A A
AA
Phillips
S M
SM
Doyle
D
D
Wolfe
R R
RR
D000284:Administration, Oral; D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage / Q000378:metabolism*; D000601:Amino Acids, Essential / Q000008:administration & dosage / Q000378:metabolism*; D003903:Deuterium; D005260:Female; D006801:Humans; D007930:Leucine / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010649:Phenylalanine / Q000378:metabolism; D005082:Physical Exertion / Q000502:physiology*
D000596:Amino Acids; D000601:Amino Acids, Essential; D009124:Muscle Proteins; D010649:Phenylalanine; D003903:Deuterium; D007930:Leucine; D008239:Lysine