Contractile protein breakdown in human leg skeletal muscle as estimated by [2H3]-3-methylhistidine: a new method.
3-Methylhistidine urinary excretion and net balances across the leg or forearm have been used as markers of contractile protein breakdown in muscle tissue. Here we investigate whether infusion of labeled 3-methylhistidine and the measurement of the arteriovenous dilution of the tracer with unlabeled 3-methylhistidine will result in more consistent and precise measurements of 3-methylhistidine rates of appearance and consequently muscle contractile protein breakdown rates in comparison with conventional arteriovenous concentration difference measurements. Six healthy volunteers were studied in the postabsorptive state and received a primed continuous infusion of 3-[2H3-methyl]- methylhistidine and L-[ring-2H5]-phenylalanine for 4 hours. 2H3-3-methylhistidine reached an isotopic steady state after 210 minutes in all subjects. Arteriovenous differences of 3-methylhistidine, measured by high-performance liquid chromatography (HPLC), showed both uptake and release from skeletal muscle, which is theoretically not likely to occur. The enrichment of 2H3-3-methylhistidine was consistently lower in the femoral vein than in the artery, and therefore a constant net release of 3-methylhistidine from the leg was observed. The mean rates of appearance for 3-methylhistidine and phenylalanine were 0.44 +/- 0.30 nmol x min(-1) x 100 mL(-1) and 11.2 +/- 5.7 nmol x min(-1) x 100 mL(-1), respectively. In summary, arteriovenous difference measurement of 2H3-3-methylhistidine enrichment is more reliable than measurement of arteriovenous difference of unlabeled 3-methylhistidine. Consequently, measuring rates of appearance from leg muscle using labeled 3-methylhistidine resulted in more consistent and accurate values of contractile protein degradation rates in human skeletal muscle.
Department of Anesthesiology and Intensive Care, Center for Surgical Sciences, Karolinska Institutet, Huddinge University Hospital, Sweden.
R F
RF
Vesali
M
M
Klaude
L
L
Thunblad
O E
OE
Rooyackers
J
J
Wernerman
D000328:Adult; D000465:Algorithms; D015415:Biomarkers; D002851:Chromatography, High Pressure Liquid; D003285:Contractile Proteins / Q000378:metabolism*; D005263:Femoral Artery / Q000378:metabolism; D005268:Femoral Vein / Q000378:metabolism; D006801:Humans; D007866:Leg / Q000098:blood supply / Q000502:physiology*; D008297:Male; D008762:Methylhistidines / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000737:chemistry / Q000378:metabolism*; D010649:Phenylalanine / Q000493:pharmacokinetics; D010991:Plethysmography; D012039:Regional Blood Flow / Q000502:physiology; D015203:Reproducibility of Results
D015415:Biomarkers; D003285:Contractile Proteins; D008762:Methylhistidines; D010649:Phenylalanine; C028118:3-methylhistidine