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A surrogate measure of whole body leucine transport across the cell membrane.

Hovorka, R, Carroll, PV, Gowrie, IJ, Jackson, NC, Russell-Jones, DL and Umpleby, AM (1999) A surrogate measure of whole body leucine transport across the cell membrane. Am J Physiol, 276 (3 Pt 1). E573-E579.

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Abstract

Based on a mass-balance model, a surrogate measure of the whole body leucine transport into and out of cells under steady-state conditions was calculated as u/DeltaTTR, where u is the infusion rate of (stable label) leucine tracer and DeltaTTR is the difference between the tracer-to-tracee ratio of extracellular and intracellular leucine. The approach was evaluated in ten healthy subjects [8 males and 2 females; age, 31 +/- 9 (SD) yr; body mass index, 24.0 +/- 1.6 kg/m2] who received a primed (7.58 micromol/kg) constant intravenous infusion (7.58 micromol. kg-1. h-1) of L-[1-13C]leucine over 180 min (7 subjects) or 240 min (3 subjects). Five subjects were studied on two occasions >/=1 wk apart to assess reproducibility. Blood samples taken during the last 30 min of the leucine infusion were used to determine plasma leucine concentration (129 +/- 35 micromol/l), TTR of leucine (9.0 +/- 1.5%), and TTR of alpha-ketoisocaproic acid (6.7 +/- 0.8%). The latter TTR was taken as the measure of the free intracellular leucine TTR. The whole body inward and outward transport was 6.66 +/- 3.82 micromol. kg-1. min-1; the rate of leucine appearance due to proteolysis was 1.93 +/- 0.24 micromol. kg-1. min-1. A positive linear relationship between the inward transport and plasma leucine was observed (P < 0.01), indicating the presence of the mass effect of leucine on its own transport. The transport was highly variable between subjects (between-subject coefficient of variation 57%) but reproducible (within-subject coefficient of variation 17%). We conclude that reproducible estimates of whole body transport of leucine across the cell membrane can be obtained under steady-state conditions with existing experimental and analytical procedures.

Item Type: Article
Authors :
NameEmailORCID
Hovorka, RUNSPECIFIEDUNSPECIFIED
Carroll, PVUNSPECIFIEDUNSPECIFIED
Gowrie, IJUNSPECIFIEDUNSPECIFIED
Jackson, NCn.jackson@surrey.ac.ukUNSPECIFIED
Russell-Jones, DLUNSPECIFIEDUNSPECIFIED
Umpleby, AMUNSPECIFIEDUNSPECIFIED
Date : March 1999
Uncontrolled Keywords : Adult, Biological Transport, Cell Membrane, Female, Homeostasis, Humans, Leucine, Male, Models, Biological, Reproducibility of Results
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 09:32
Last Modified : 17 May 2017 14:43
URI: http://epubs.surrey.ac.uk/id/eprint/824101

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