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Anomeric specificity of d-[U-14C]glucose incorporation into glycogen in rat hemidiaphragms

par Zhang, Ying ;Courtois, Philippe ;Sener, Abdullah ;Malaisse, Willy
Référence Biochimie, 86, 12, page (913-918)
Publication Publié, 2004

Article révisé par les pairs

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Résumé :

The anomeric specificity of d-[U-14C]glucose incorporation into glycogen in rat hemidiaphragms was investigated. For this purpose, the hemidiaphragms were preincubated for 30:min at 37:°C and then incubated for 5:min at the same temperature in the presence of α- or β-d-[U- 14C]glucose. The concentrations of d-glucose (5.6 or 8.8:mM) and insulin (0 or 10:mU/ml) were identical during the preincubation and incubation periods. The incubation medium was prepared in D2O/H2O (3:1, v/v) in order to delay the interconversion of the d-glucose anomers. In addition to glycogen labelling, the output of radioactive acidic metabolites was also measured. Insulin caused a preferential stimulation of glycogen labelling relative to glycolysis. Such was not the case in response to a rise in d-glucose concentration. At 5.6:mM d-glucose and whether in the presence or absence of insulin, both glycogen labelling and glycolysis were lower with α-d-glucose than with β-d-glucose suggesting a higher rate of β-d-glucose than α-d-glucose transport across the plasma membrane. A mirror image was found at 8.8:mM d-glucose, especially in the absence of insulin. At this close-to-physiological hexose concentration, insulin lowered the α/β ratio for glycogen labelling. On the contrary, the rise in d-glucose concentration increased such a ratio. Since such a rise is probably little affected by any possible anomeric difference in d-glucose transport across the plasma membrane, the present results strongly suggest that the intracellular factors regulating net glycogen synthesis, as well as glycolytic flux, display obvious preference for α-d-glucose. © 2004 Elsevier SAS. All rights reserved.