title: Aminoacyl-tRNA enrichment after a flood of labeled phenylalanine: insulin effect on muscle protein synthesis.
abstract: Muscle protein synthesis in dogs measured by flooding with L-[(2)H(5)]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-[(2)H(5)]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.
authors.affiliation: Department of Surgery, State University of New York, Stony Brook, New York 11794-8191, USA. Giuseppe.Caso@stonybrook.edu
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Caso
authors.forename: G Charles
authors.initials: GC
authors.lastname: Ford
authors.forename: K Sreekumaran
authors.initials: KS
authors.lastname: Nair
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Garlick
authors.forename: Margaret A
authors.initials: MA
authors.lastname: McNurlan
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000493:pharmacokinetics; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003903:Deuterium; D004285:Dogs; D005947:Glucose / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000097:blood / Q000494:pharmacology*; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D010649:Phenylalanine / Q000097:blood / Q000493:pharmacokinetics*; D011498:Protein Precursors / Q000096:biosynthesis; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009124:Muscle Proteins; D011498:Protein Precursors; D012346:RNA, Transfer, Amino Acyl; D010649:Phenylalanine; D003903:Deuterium; D005947:Glucose