Glutamine transport in C6 glioma cells.
Glutamine transport across the cell membranes of a variety of mammalian tissues is mediated by at least four transport systems: a sodium-independent system L, and sodium-dependent systems A, ASC and N, the latter occurring in different tissue-specific variants. In this study we assessed the contribution of these systems to the uptake of [(3)H]glutamine in C6 rat glioma cells. The sodium-dependent uptake, which accounted for more than 80% of the total uptake, was not inhibited by 2-methylaminoisobutyric acid (MeAIB), indicating that system A was inactive, possibly being depressed by glutamine present in the culture medium. About 80% of the sodium-dependent uptake was mediated by system ASC, which differed from system ASC common to other CNS- and non-CNS tissues by its pH-dependence and partial lithium tolerance. The residual 20% of sodium-dependent uptake appeared to be mediated by system N, which was identified as a component resistant to inhibition by MeAIB+threonine. The system N in C6 cells appeared to be neither fully compatible with the neuronal system Nb, nor with the N system described in astrocytes: it differed from the former in being strongly inhibited by histidine and showing fair tolerance for lithium, and from the latter in its pH-insensitivity and strong inhibition by glutamate. The sodium-independent glutamine uptake differed from the astrocytic or neuronal uptake in its relatively weak inhibition by system L substrates and a strong inhibition by system ASC substrates, indicating a possible contribution of a variant of the ASC system.
Dolińska
M
M
Department of Neurotoxicology, Medical Research Centre, Polish Academy of Sciences, Warsaw.
Dybel
A
A
Albrecht
J
J
D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism*; D005910:Glioma / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018021:Lithium Chloride / Q000494:pharmacology; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism; D051381:Rats; D013912:Threonine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D009363:Neoplasm Proteins; D005973:Glutamine; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D013912:Threonine; D018021:Lithium Chloride