title: Uptake of L-glutamine into synaptosomes. Is the gamma-glutamyl cycle involved?
abstract: Transport of L-glutamine into rat cortical synaptosomes has been investigated by (14C)L-glutamine uptake experiments. This amino acid enters synaptosomes both by an active carrier mediated system, which may be the result of gamma-glutamyl cycle activity and by a Na+-dependent transport system. This view is supported by the following observations: a) as demonstrated previously (10), glutamine inside synaptosomes reaches concentrations higher than those of the incubation medium, and initial rates of uptake approach saturation kinetics; b) the uptake of glutamine is inhibited by uncouplers; c) the uptake is inhibited by methionine sulfoximine, a suicide-inhibitor of an enzyme of the gamma-glutamyl cycle; d) the initial rate of uptake is lowered by decreasing the Na+-level of the incubation medium or by adding ouabain. The validity of this hypothesis is discussed.
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D008297:Male; D008717:Methionine Sulfoximine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000378:metabolism
chemical_list: D000596:Amino Acids; D005973:Glutamine; D008717:Methionine Sulfoximine; D012964:Sodium; D005723:gamma-Glutamyltransferase