Postexercise net protein synthesis in human muscle from orally administered amino acids

Citation

Tipton K, Ferrando AA, Phillips SM, Doyle DJ & Wolfe RR (1999) Postexercise net protein synthesis in human muscle from orally administered amino acids. American Journal of Physiology - Endocrinology and Metabolism, 276 (4), pp. E628-E634. http://ajpendo.physiology.org/content/276/4/E628.long

Abstract
We examined the response of net muscle protein synthesis to ingestion of amino acids after a bout of resistance exercise. A primed, constant infusion ofl-[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), and3) a placebo solution (PLA). Arterial amino acid concentrations increased ∼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 less than 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.

Keywords
muscle protein synthesis; muscle protein breakdown; resistance exercise; stable isotopes

Journal
American Journal of Physiology - Endocrinology and Metabolism: Volume 276, Issue 4