The single-biopsy approach in determining protein synthesis in human slow-turning-over tissue: use of flood-primed, continuous infusion of amino acid tracers.
Muscle protein synthesis (MPS) rate is determined conventionally by obtaining two or more tissue biopsies during a primed, continuous infusion of a stable isotopically labeled amino acid. The purpose of the present study was to test whether tracer priming given as a flooding dose, thereby securing an instantaneous labeling of the tissue pools of free tracee amino acids, followed by a continuous infusion of the same tracer to maintain tracer isotopic steady state, could be used to determine the MPS rate over a prolonged period of time by obtaining only a single tissue biopsy. We showed that the tracer from the flood prime appeared immediately in the muscle free pool of amino acids and that this abundance could be kept constant by a subsequent continuous infusion of the tracer. When using phenylalanine as tracer, the flood-primed, continuous infusion protocol does not stimulate the MPS rate per se. In conclusion, the flood-primed, continuous infusion protocol using phenylalanine as tracer can validly be used to measure the protein synthesis rate in human in vivo experiments by obtaining only a single tissue biopsy after a prolonged infusion period.
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark larsh@sund.ku.dk.
Lars
L
Holm
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
Søren
S
Reitelseder
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and.
Kasper
K
Dideriksen
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and.
Rie H
RH
Nielsen
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and.
Jacob
J
Bülow
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; and.
Michael
M
Kjaer
D000465:Algorithms; D000596:Amino Acids / Q000737:chemistry*; D001706:Biopsy / Q000379:methods*; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics; D003238:Connective Tissue / Q000737:chemistry / Q000378:metabolism; D003627:Data Interpretation, Statistical; D006801:Humans; D007262:Infusions, Intravenous; D007651:Keto Acids / Q000097:blood; D007930:Leucine / Q000032:analysis / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D010649:Phenylalanine / Q000097:blood; D014176:Protein Biosynthesis / Q000502:physiology*; D011849:Radioactive Tracers; D055815:Young Adult
D000596:Amino Acids; D007651:Keto Acids; D009124:Muscle Proteins; D011849:Radioactive Tracers; D010649:Phenylalanine; C013082:alpha-ketoisocaproic acid; D003094:Collagen; D007930:Leucine
fractional synthesis rate; protein turnover; stable isotope; tracer administration