TY - JOUR
T1 - Aminoacyl-tRNA enrichment after a flood of labeled phenylalanine
T2 - Insulin effect on muscle protein synthesis
AU - Caso, Giuseppe
AU - Charles Ford, G.
AU - Sreekumaran Nair, K.
AU - Garlick, Peter J.
AU - McNurlan, Margaret A.
PY - 2002
Y1 - 2002
N2 - Muscle protein synthesis in dogs measured by flooding with L-[2H5] phenylalanine (70 mg/kg) was significantly stimulated by infusion of insulin with amino acids. The stimulation of muscle protein synthesis was similar when calculated from the enrichment of phenylalanyl-tRNA (61 ± 10%, P < 0.001), plasma phenylalanine (61 ± 10%, P < 0.001), or tissue fluid phenylalanine (54 ± 10%, P < 0.001). The time course for changes in enrichment of L-[2H5]phenylalanine throughout the flooding period was determined for plasma, tissue fluid, and phenylalanyl-tRNA in the basal state and during the infusion of insulin with amino acids. Enrichments of plasma free phenylalanine and phenylalanyl-tRNA were equalized between 20 and 45 min, although the enrichment of phenylalanyl-tRNA was lower at early time points. Rates of muscle protein synthesis obtained with the flooding method and calculated from plasma phenylalanine enrichment were comparable to those calculated from phenylalanyl-tRNA and also to those obtained previously with a continuous infusion of phenylalanine with phenylalanyl-tRNA as precursor. This study confirms that, with a bolus injection of labeled phenylalanine, the enrichment of aminoacyl-tRNA, the true precursor pool for protein synthesis, can be assessed from more readily sampled plasma phenylalanine.
AB - Muscle protein synthesis in dogs measured by flooding with L-[2H5] phenylalanine (70 mg/kg) was significantly stimulated by infusion of insulin with amino acids. The stimulation of muscle protein synthesis was similar when calculated from the enrichment of phenylalanyl-tRNA (61 ± 10%, P < 0.001), plasma phenylalanine (61 ± 10%, P < 0.001), or tissue fluid phenylalanine (54 ± 10%, P < 0.001). The time course for changes in enrichment of L-[2H5]phenylalanine throughout the flooding period was determined for plasma, tissue fluid, and phenylalanyl-tRNA in the basal state and during the infusion of insulin with amino acids. Enrichments of plasma free phenylalanine and phenylalanyl-tRNA were equalized between 20 and 45 min, although the enrichment of phenylalanyl-tRNA was lower at early time points. Rates of muscle protein synthesis obtained with the flooding method and calculated from plasma phenylalanine enrichment were comparable to those calculated from phenylalanyl-tRNA and also to those obtained previously with a continuous infusion of phenylalanine with phenylalanyl-tRNA as precursor. This study confirms that, with a bolus injection of labeled phenylalanine, the enrichment of aminoacyl-tRNA, the true precursor pool for protein synthesis, can be assessed from more readily sampled plasma phenylalanine.
KW - Amino acids
KW - Dog
KW - Flooding technique
KW - Ketoisocaproic acid
KW - L-[H]phenylalanine
KW - Stable isotopes
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U2 - 10.1152/ajpendo.00215.2001
DO - 10.1152/ajpendo.00215.2001
M3 - Article
C2 - 11934667
AN - SCOPUS:0036086946
SN - 0193-1849
VL - 282
SP - E1029-E1038
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 5 45-5
ER -