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LABELLING OF BRAIN PROTEINS AT EARLY PERIODS AFTER SUBCUTANEOUS INJECTION OF A MIXTURE OF [U‐ 14 C]GLUCOSE AND [ 3 H]GLUTAMATE
Author(s) -
Gaitonde M. K.,
Harms Viki,
Evans Gwyneth
Publication year - 1978
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1978.tb07835.x
Subject(s) - glutamine , glutamate receptor , amino acid , labelling , glutamic acid , biochemistry , alanine , biology , chemistry , medicine , endocrinology , receptor
Abstract— To obtain evidence of the site of conversion of [U‐ 14 C]glucose into glutamate and related amino acids of the brain, a mixture of [U‐ 14 C]glucose and [ 3 H]glutamate was injected subcutaneously into rats. [ 3 H]Glutamate gave rise to several 3 H‐labelled amino acids in rat liver and blood; only 3 H‐labelled glutamate, glutamine or γ‐aminobutyrate were found in the brain. The specific radioactivity of [ 3 H]glutamine in the brain was higher than that of [ 3 H]glutamate indicating the entry of [ 3 H]glutamate mainly in the ‘small glutamate compartment’. The 14 C‐labelling pattern of amino acids in the brain and liver after injection of [U‐ 14 C]glucose was similar to that previously reported (G aitonde et al. , 1965). The specific radioactivity of [ 14 C]glutamine in the blood and liver after injection of both precursors was greater than that of glutamate between 10 and 60 min after the injection of the precursors. The extent of labelling of alanine and aspartate was greater than that of other amino acids in the blood after injection of [U‐ 14 C]glucose. There was no labelling of brain protein with [ 3 H]glutamate during the 10 min period, but significant label was found at 30 and 60 min. The highest relative incorporation of [ 14 C]glutamate and [ 14 C]aspartate in rat brain protein was observed at 5 min after the injection of [U‐ 14 C]glucose. The results have been discussed in the context of transport of glutamine synthesized in the brain and the site of metabolism of [U‐ 14 C]glucose in the brain.