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Comparison of Rates of Local Cerebral Glucose Utilization Determined with Deoxy[l‐ 14 C]glucose and Deoxy[6‐ 14 C]glucose
Author(s) -
Dienel Gerald A.,
Cruz Nancy F.,
Nakanishi Hajime,
Melzer Peter,
Moulis Penny,
Sokoloff Louis
Publication year - 1992
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.1471-4159.1992.tb08457.x
Subject(s) - pentose phosphate pathway , hexose , transketolase , carbohydrate metabolism , biochemistry , metabolism , glucose 6 phosphate , in vivo , chemistry , glucose uptake , glycolysis , metabolic pathway , biology , endocrinology , insulin , enzyme , microbiology and biotechnology
The activity of the pentose phosphate shunt pathway in brain is thought to be linked to neurotransmitter metabolism, glutathione reduction, and synthetic pathways requiring NADPH. There is currently no method available to assess flux of glucose through the pentose phosphate pathway in localized regions of the brain of conscious animals in vivo. Because metabolites of deoxy[l‐ 14 C]glucose are lost from brain when the experimental period of the deoxy[ 14 C]glucose method exceeds 45 min, the possibility was considered that the loss reflected activity of this shunt pathway and that this hexose might be used to assay regional pentose phosphate shunt pathway activity in brain. Decarboxylation of deoxy[l‐ 14 C]glucose by brain extracts was detected in vitro, and small quantities of 14 C were recovered in the 6‐phosphodeoxygluconate fraction when deoxy[ 14 C]glucose metabolites were isolated from freeze‐blown brains and separated by HPLC. Local rates of glucose utilization determined with deoxy[l‐ 14 C]glucose and deoxy[6‐ 14 C]glucose were, however, similar in 20 brain structures at 45,60,90 , and 120 min after the pulse, indicating that the rate of loss of 14 CO 2 from deoxy[l‐ 14 C]glucose‐6‐phosphate in normal adult rat brain is too low to permit assay pentose phosphate shunt activity in vivo. Further metabolism of deoxy[l‐ 14 C]glucose‐6‐phosphate via this pathway does not interfere during routine use of the deoxyglu‐cose method or explain the progressive decrease in calculated metabolic rate when the experimental period exceeds 45 min.