Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-3C]leucine.
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.
D000293:Adolescent; D000328:Adult; D002245:Carbon Dioxide / Q000502:physiology; D002250:Carbon Radioisotopes; D006801:Humans; D007263:Infusions, Parenteral; D007930:Leucine / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D008433:Mathematics; D012119:Respiration; D013997:Time Factors
D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D007930:Leucine