TY - JOUR
T1 - Increased concentration of tracee affects estimates of muscle protein synthesis
AU - Caso, Giuseppe
AU - Ford, G. Charles
AU - Sreekumaran Nair, K.
AU - Vosswinkel, James A.
AU - Garlick, Peter J.
AU - McNurlan, Margaret A.
PY - 2001
Y1 - 2001
N2 - Muscle protein synthesis was measured by infusion of L-[2H5]phenylalanine in two groups of anesthetized dogs, before and during infusion of insulin with euaminoacidemia, and with differing concentrations of unlabeled phenylalanine (tracee). With the infusion of insulin, muscle protein synthesis increased 39 ± 12% based on phenylalanyl-tRNA. Calculation with plasma phenylalanine enrichment overestimated insulin stimulation by 40% (56 ± 12 vs. 39 ± 12%). Raising the concentration of plasma phenylalanine twofold during infusion of insulin further increased the apparent stimulation of muscle protein synthesis based on plasma relative to phenylalanyl-tRNA by 225% (65 ± 19 vs. 20 ± 14%, P < 0.001). In both experiments, the stimulation of synthesis rates calculated from phenylalanine enrichment within the muscle was closer to that from phenylalanyl-tRNA (48 ± 19%, experiment 1; 30 ± 14%, experiment 2). Results indicate that the enrichment of a labeled amino acid within plasma and tissue amino acid pools is affected by the concentration of tracee infused. Increasing the concentration of tracee overestimates the insulin-mediated stimulation of muscle protein synthesis when amino acid pools other than aminoacyl-tRNA are used as the precursor enrichment.
AB - Muscle protein synthesis was measured by infusion of L-[2H5]phenylalanine in two groups of anesthetized dogs, before and during infusion of insulin with euaminoacidemia, and with differing concentrations of unlabeled phenylalanine (tracee). With the infusion of insulin, muscle protein synthesis increased 39 ± 12% based on phenylalanyl-tRNA. Calculation with plasma phenylalanine enrichment overestimated insulin stimulation by 40% (56 ± 12 vs. 39 ± 12%). Raising the concentration of plasma phenylalanine twofold during infusion of insulin further increased the apparent stimulation of muscle protein synthesis based on plasma relative to phenylalanyl-tRNA by 225% (65 ± 19 vs. 20 ± 14%, P < 0.001). In both experiments, the stimulation of synthesis rates calculated from phenylalanine enrichment within the muscle was closer to that from phenylalanyl-tRNA (48 ± 19%, experiment 1; 30 ± 14%, experiment 2). Results indicate that the enrichment of a labeled amino acid within plasma and tissue amino acid pools is affected by the concentration of tracee infused. Increasing the concentration of tracee overestimates the insulin-mediated stimulation of muscle protein synthesis when amino acid pools other than aminoacyl-tRNA are used as the precursor enrichment.
KW - Amino acids
KW - Aminoacyl-tRNA
KW - Insulin
KW - L-[H]phenylalanine
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U2 - 10.1152/ajpendo.2001.280.6.e937
DO - 10.1152/ajpendo.2001.280.6.e937
M3 - Article
C2 - 11350775
AN - SCOPUS:0034979258
SN - 0193-1849
VL - 280
SP - E937-E946
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 6 43-6
ER -