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Acid Lability of Metabolites of 2‐Deoxyglucose in Rat Brain: Implications for Estimates of Kinetic Parameters of Deoxyglucose Phosphorylation and Transport Between Blood and Brain
Author(s) -
Dienel Gerald A.,
Cruz Nancy F.,
Mori Kentaro,
Sokoloff Louis
Publication year - 1990
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.1471-4159.1990.tb01981.x
Subject(s) - deoxyglucose , chemistry , hexose , ethanol , lability , biochemistry , metabolism , chromatography , metabolite , enzyme
The steady‐state brain/plasma distribution ratios of [ 14 C]deoxyglucose ([ 14 C]DG) for hypoglycemic rats previously determined by measurement of DG concentrations in neutralized acid extracts of freeze‐blown brain and plasma exceeded those predicted by simulations of kinetics of the DG model. Overestimation of the true size of the precursor pool of [ 14 C]DG for transport and phosphorylation could arise from sequestration of [ 14 C]DG within brain compartments and/or instability of metabolites of [ 14 C] DG and regeneration of free [ 14 C]DG during the experimental period or extraction procedure. In the present study, the concentrations of [ 14 C]DG and glucose were compared in samples of rat brain and plasma extracted in parallel with perchloric acid or 65% ethanol containing phosphate‐buffered saline. The concentrations of both hexoses in acid extracts of brain were higher than those in ethanol, whereas hexose contents of plasma were not dependent on the extraction procedure. The magnitude of overestimation of DG content (about 1.2 to fourfold) varied with glucose level and was highest in extracts isolated from hypoglycemic rats; contamination of the [ 14 C]DG fraction with 14 C‐labeled nonacidic metabolites also contributed to this overestimation. Glucose concentrations in acid extracts of brain exceeded those of the ethanol extracts by < 40% for normal and hypoglycemic rats.