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Glutamine transport in human skeletal muscle
A Ahmed1, D L Maxwell, P M Taylor
1Department of Anatomy and Physiology, University of Dundee, Scotland.
The American Journal of Physiology
|June 1, 1993
Summary
Human skeletal muscle vesicles exhibit stereospecific, sodium-dependent glutamine transport with distinct kinetic properties across different muscle types. This transporter shares similarities but also shows key differences compared to rat skeletal muscle transporters.
Area of Science:
- Biochemistry
- Physiology
- Molecular Biology
Background:
- Sarcolemmal vesicles are crucial for studying muscle cell membrane transport.
- Glutamine is a vital amino acid for skeletal muscle function and metabolism.
- Understanding amino acid transporters is key to muscle physiology.
Purpose of the Study:
- To characterize the kinetic properties and substrate specificity of glutamine transport in human skeletal muscle sarcolemmal vesicles.
- To compare the human glutamine transporter with known transporters in other species, particularly rat skeletal muscle.
Main Methods:
- Isolation of sarcolemmal vesicles from human skeletal muscle.
- Assay of enzyme markers for vesicle enrichment (5'-nucleotidase, K-stimulated phosphatase).
- Measurement of [3H]glutamine and other amino acid transport kinetics, including sodium dependence, stereospecificity, and pH sensitivity.
Main Results:
- Vesicles showed significant enrichment of sarcolemmal markers.
- [3H]glutamine transport was stereospecific, sodium-dependent, and rheogenic, indicating Na-glutamine cotransport.
- Transport kinetics varied between different human skeletal muscles (e.g., tibialis anterior vs. gluteus maximus).
- Glutamine transport showed sensitivity to pH and inhibition by specific amino acids, with cysteine showing unusual effects at high concentrations.
Conclusions:
- Human skeletal muscle possesses a distinct glutamine transporter with both Na-dependent and Na-independent components.
- Significant kinetic heterogeneity exists for this transporter across different muscle types.
- The identified transporter exhibits both similarities and notable differences compared to the rat skeletal muscle System Nm transporter.