Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-3C]leucine

Am J Physiol. 1980 May;238(5):E473-9. doi: 10.1152/ajpendo.1980.238.5.E473.


Leucine metabolism in vivo can be determined from a primed, continuous infusion of L-[1-13C]leucine by measuring, at isotopic steady state, plasm [-13C]leucine enrichment, expired 13CO2 enrichment, and CO2 production rate. With an appropriate priming dose of L-[1-13C]leucine and NaH13CO3, isotopic steady state is reached in less than 2 h, and the infusion is completed in 4 h. The method can determine rates of leucine turnover, oxidation, and incorporation into protein with typical relative uncertainties of 2, 10, and 4%, respectively. The method requires no more than 1 ml of blood and uses stable isotope rather than radioisotope techniques. Thus, the method is applicable to studies of human beings of all ages. L-[1-13C]leucine may be infused with a second amino acid labeled with 15N for simultaneous determination of the kinetics of two amino acids.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Carbon Dioxide / physiology
  • Carbon Radioisotopes
  • Humans
  • Infusions, Parenteral
  • Leucine / administration & dosage
  • Leucine / metabolism*
  • Male
  • Mathematics
  • Respiration
  • Time Factors


  • Carbon Radioisotopes
  • Carbon Dioxide
  • Leucine