Sub‐compartmentation of the ‘cytosolic’ glucose 6‐phosphate pool in cultured rat hepatocytes

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Abstract
[14C]Glucose release either from endogenous 14C‐prelabelled glycogen or from added 14C‐labelled glucose 6‐phosphate was measured in filipin‐treated, permeabilized hepatocytes in 48 h culture. [14C]Glucose output from prelabelled glycogen was not altered by the addition of 5 mM glucose 6‐phospate to the incubation medium. Conversely, [14C]glucose release from 5 mM labelled glucose 6‐phosphate was not influenced by different glycogen concentrations in the cells. Moreover, in the permeabilized cells the anion transport inhibitor DIDS (4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid) inhibited only the liberation of [14C]glucose from labelled glucose 6‐phosphate but not from glycogen. It is therefore concluded that there exist at least 2 separate, mutually non‐accessible glucose 6‐phosphate pools in cultured rat hepatocytes, one linked to glycogenolysis and the other to gluconeogenesis.