Protein synthesis in isolated perfused rat skeletal muscle. Contribution of intra- and extracellular amino acid pools

Protein synthesis was measured in perfused rat skeletal muscle using [14C]lysine in the presence of increasing amounts of lysine in the perfusate. The results obtained clearly indicated that both the extracellular and intracellular pools of amino acids act as direct precursors for protein synthesis and analysis of the data, according to O'Hara et al. (J. molec. cell. Cardiol. 13, 925-940, 1981) further indicated that extracellular sources of lysine supplied 64 and 81% of the lysine incorporated in the absence and presence of insulin, respectively. The rate of protein synthesis were assessed to be 0.22 mumol lysine incorporated g-1 muscle per 3 hr of perfusion increasing to 1.0 mumol g-1 3 hr-1 in the presence of insulin.