The aerobic incubation of rat brain cortex slices leads to rapid incorporation of metabolite carbon from both glucose-U-C14 and fructose-U-C14 into glutamic acid, aspartic acid, glutamine, alanine, and γ-aminobutyric acid (γABA). Use of labeled glutamic acid results in a greater incorporation into aspartic acid, and no labeling of alanine. The incorporation from γABA-1-C14 is lowest, and does not result in labeling of alanine. Both hydroxylamine and aminooxyacetic acid (AOAA) abolish the incorporation of metabolite carbon into γABA and alanine, and diminish that of glutamine, with labeling of aspartic acid diminished with fructose as the substrate. Both inhibitors abolish all amino acid labeling from γABA-1-C14, and exert differing effects on incorporation from glutamic acid, depending on the presence or absence of glucose. The respiration of brain cortex slices is markedly diminished by AOAA and by the higher concentration of hydroxylamine, whereas with fructose 0.5 mM hydroxylamine is also effective. Similar inhibitory effects are observed on the C14O2 production. The inhibitory effects of AOAA on incorporation of metabolite carbon from glucose, the respiration, and the carbon dioxide production are reversed by pyridoxal phosphate, and spectrophotometric data indicate that this is due to complex formation between the vitamin and the inhibitor.
