In vivo muscle amino acid transport involves two distinct processes

Sharon Miller, David Chinkes, David A. MacLean, Dennis Gore, Robert R. Wolfe

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

We have tested the hypothesis that transit through the interstitial fluid, rather than across cell membranes, is rate limiting for amino acid uptake from blood into muscle in human subjects. To quantify muscle transmembrane transport of naturally occurring amino acids, we developed a novel 4-pool model that distinguishes between the interstitial and intracellular fluid compartments. Transport kinetics of phenylalanine, leucine, lysine, and alanine were quantified using tracers labeled with stable isotopes. The results indicate that interstitial fluid is a functional compartment insofar as amino acid kinetics are concerned. In the case of leucine and alanine, transit between blood and interstitial fluid was potentially rate limiting for muscle amino acid uptake and release in the postabsorptive state. For example, in the case of leucine, the rate of transport between blood and interstitial fluid compared with the corresponding rate between interstitial fluid and muscle was 247 ± 36 vs. 610 ± 95 nmol·min-1·100 ml leg-1, respectively (P < 0.05). Our results are consistent with the process of diffusion governing transit from blood to interstitial fluid without selectivity, and of specific amino acid transport systems with varying degrees of efficiency governing transit from interstitial fluid to muscle. These results imply that changes in factors that affect the transit of amino acids from blood through interstitial fluid, such as muscle blood flow or edema, could play a major role in controlling the rate of muscle amino acid uptake.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume287
Issue number1 50-1
DOIs
StatePublished - Jul 2004

Fingerprint

Extracellular Fluid
Muscle
Amino Acids
Muscles
Fluids
Blood
Leucine
Alanine
Intracellular Fluid
Amino Acid Transport Systems
Kinetics
Cell membranes
Phenylalanine
Isotopes
Lysine
Edema
Leg
Cell Membrane

Keywords

  • Interstitial fluid
  • Microdialysis
  • Stable isotopes

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

In vivo muscle amino acid transport involves two distinct processes. / Miller, Sharon; Chinkes, David; MacLean, David A.; Gore, Dennis; Wolfe, Robert R.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 287, No. 1 50-1, 07.2004.

Research output: Contribution to journalArticle

Miller, Sharon ; Chinkes, David ; MacLean, David A. ; Gore, Dennis ; Wolfe, Robert R. / In vivo muscle amino acid transport involves two distinct processes. In: American Journal of Physiology - Endocrinology and Metabolism. 2004 ; Vol. 287, No. 1 50-1.
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