Na(+)-dependent high-affinity uptake of L-glutamate in cultured fibroblasts.
Uptake of 1 microM [3H]L-glutamate by cultured 3T3 fibroblasts was strongly dependent on extracellular Na+; it was reduced by elevated concentrations of K+ (60 mM) but it was not influenced by variations in the concentration of Ca2+ (0-9.6 mM). D- and L-Asparate, D- and L-threo-3-hydroxyaspartate DL-threo-3-methylaspartate and a few other glutamate derivatives and analogues inhibited the uptake but several close analogues of L-glutamate (including D-glutamate) had no effect, implying that the uptake system is highly structurally selective. The recently identified inhibitor of glutamate uptake in synaptosomal preparations, L-trans-pyrrolidine-2,4-dicarboxylate, was also among the inhibitors. Apparent Km of the uptake was found to be less than 10 microM. The present observations indicate that Na(+)-dependent 'high-affinity' uptake of L-glutamate may appear in structures which are apparently unrelated to glutamatergic synaptic transmission in the CNS.
Department of Anatomy, University of Sydney, NSW, Australia.
V J
VJ
Balcar
D016475:3T3 Cells / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004622:Embryo, Mammalian; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D007700:Kinetics; D051379:Mice; D012964:Sodium / Q000494:pharmacology*
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D018698:Glutamic Acid; D012964:Sodium; D002118:Calcium