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Metabolic Fluxes Between [ 14 C]2‐Deoxy‐D‐Glucose and [ 14 C]2‐Deoxy‐D‐Glucose‐6‐Phosphate in Brain In Vivo
Author(s) -
Huang MingTa,
Veech Richard L.
Publication year - 1985
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.1471-4159.1985.tb05450.x
Subject(s) - deoxyglucose , reaction rate constant , hexokinase , chemistry , elimination rate constant , in vivo , phosphate , reaction rate , glucose 6 phosphate , kinetics , radiochemistry , glycolysis , metabolism , biochemistry , medicine , pharmacokinetics , enzyme , physics , catalysis , biology , volume of distribution , microbiology and biotechnology , quantum mechanics
The rates of the phosphorylation and dephosphorylation of 2‐deoxyglucose were measured in rat brain in vivo using tracer kinetic techniques. The rate constant for each reaction was estimated from two separate experiments with different protocols for tracer administration. Tracer amounts of [1‐ 14 C]2‐deoxyglucose (1 μCi) were injected through the internal carotid artery (intraarterial experiment), or through the atrium (intravenous experiment). Brains were sampled by freeze‐blowing at various times after the injection. In the intraarterial experiment, the rate constant for the forward reaction from 2‐deoxyglucose to 2‐deoxyglucose phosphate was calculated by dividing the initial rate of 2‐deoxyglucose phosphate production by the 2‐deoxyglucose content in brain. The rate constant for the reverse reaction from 2‐deoxyyglucose phosphate to 2‐deoxyglucose was calculated from the decay constant of 2‐deoxyglucose phosphate. The rate constants estimated were 10.1 ± 1.4%/min (SD) and 3.00 ± 0.01%/min (SD), respectively, for the forward and reverse reactions. In the intravenous experiment, rate constants for both reactions were estimated by compartmental analysis. By fitting data to program SAAM‐27, the rate constants for the forward and reverse reactions were estimated as 11.4 ± 0.4%/min (SD) and 5.1 ± 0.4%/min (SD), respectively. The rate constants determined were compared to those for the reactions between glucose and glucose‐6‐phosphate, estimated previously from labeled glucoses. It is concluded that the rate of glucose utilization measured by the 2‐deoxyglucose method reflects the rate of the hexokinase reaction and not the rate of glucose utilization or brain energy utilization.