Metabolic Compartmentation of the Glutamate - Glutamine System: Glial Contribution
In the two previous symposia on Metabolic Compartmentation in Brain (Balazs and Cremer, 1973; Berl et al., 1975) it had been suggested by several of the participants that the several pools of glutamate and related metabolites revealed by the use of labelled tracers are probably localized in different cell types, namely neurons and glia. The nerve endings were suggested as a possible third compartment although in a two compartment model they were included with the neurons and dendrites. The two compartment model has been relatively successful in fitting most of the experimental data probably because the focus has been on the relationship of glutamate to glutamine metabolism. Since the nerve endings do not appear to be particularly active in glutamine formation their consideration as a separate pool could be neglected in the interpretation of the experimental data. However, when the formation of GABA from a variety of different labelled precursors such as acetate (Berl et al., 1970), glucose (Gaitonde, 1965; Cremer 1973) and glutamine (Berl et al., 1961; Shank and Aprison, 1977) as well as the location of glutamate decarboxylase in nerve endings (Saito et al., 1974) is considered it as evident that a separate pool of glutamate for GABA formation is required.
KeywordsCitrate Bicarbonate Glutamine Neurol Cytosol
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