title: Compartmental approach for evaluation of plasma kinetics and (13)co(2)-exhalation after oral loading with L-[1-(13)c]leucine.
abstract: Abstract   A seven compartment model was applied for evaluation of oral L-[1-(13)C]leucine loading tests (38 μmol/kg body wt.) in healthy volunteers. The model comprises transport and absorption in stomach and gut into a central L-leucine-compartment which is connected to a protein compartment and to the compartment of the corresponding 2-oxo acid. CO(2) release from the latter occurs in a fast and a slow compartment into the central CO(2) compartment for exhalation. Using the fmins routine of MATLAB for parameter estimation, a good agreement was obtained between calculated and actually measured kinetics of (13)C-labelled metabolites and a mean in vivo L-leucine oxidation of 0.365 ± 0.071 μmol/kg per min (n = 5) was computed. Plausibility of the model was checked by predicting in vivo leucine oxidation rates from primed continuous infusion tests (priming: L-[1-(13)C]leucine, 5 μmol/kg; NaH(13)CO(2), 1.2 μmol/kg; infusion: L-[1-(13)C]leucine, 5 μmol/kg per h). In 5 tested volunteers, the experimental L-leucine oxidation rate amounted to 0.358 ± 0.105 μmol/kg per min versus predicted 0.324±0.099 μmol/kg per min. Possible causes for some observed intraindividual variations are discussed.
authors.affiliation: a    Kinderklinik Eberhard-Karls-Universität   ,  Tübingen ,    Deutschland.
authors.forename: A
authors.initials: A
authors.lastname: Bodner
authors.forename: W
authors.initials: W
authors.lastname: Renn
authors.forename: U
authors.initials: U
authors.lastname: Wendel
authors.forename: P
authors.initials: P
authors.lastname: Schadewaldt