期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：14
页码：8235-8240
DOI：10.1073/pnas.96.14.8235
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Recent 13C NMR studies in rat models have shown that the glutamate/glutamine cycle is highly active in the cerebral cortex and is coupled to incremental glucose oxidation in an {approx}1:1 stoichiometry. To determine whether a high level of glutamatergic activity is present in human cortex, the rates of the tricarboxylic acid cycle, glutamine synthesis, and the glutamate/glutamine cycle were determined in the human occipital/parietal lobe at rest. During an infusion of [1-13C]-glucose, in vivo 13C NMR spectra were obtained of the time courses of label incorporation into [4-13C]-glutamate and [4-13C]-glutamine. Using a metabolic model we have validated in the rat, we calculated a total tricarboxylic acid cycle rate of 0.77 {+/-} 0.07 {micro}mol/min/g (mean {+/-} SD, n = 6), a glucose oxidation rate of 0.39 {+/-} 0.04 {micro}mol/min/g, and a glutamate/glutamine cycle rate of 0.32 {+/-} 0.05 {micro}mol/min/g (mean {+/-} SD, n = 6). In agreement with studies in rat cerebral cortex, the glutamate/glutamine cycle is a major metabolic flux in the resting human brain with a rate {approx}80% of glucose oxidation.
