Glycogen is mobilized during the disposal of peroxides by cultured astroglial cells from rat brain

Regeneration of reduced nicotinamide adenine dinucleotide phosphate (NADPH) is essential for the activity of glutathione redox cycling during cellular peroxide detoxification. In order to test for a function of astroglial gly cogen to serve as endogenous precursor for glucose-6-phosphate, the substra te for the regeneration of NADPH by the pentose phosphate pathway, the cont ent of glycogen in astroglia-rich primary cultures derived from the brains of newborn rats was determined after application of peroxides. In the prese nce of hydrogen peroxide or cumene hydroperoxide in concentrations of 200 m u M glycogen was mobilized with a half-life of 16 min in incubation medium containing 20 mM glucose, whereas in the absence of peroxides the glycogen content decreased more slowly with a half-life of 42 min. After 30 min of i ncubation with or without peroxides 30 and 73%, respectively, of the initia l glycogen content was found. The degree of glycogen mobilization was reduc ed by lowering the initial concentration of the peroxides. These results de monstrate that in astroglial cells (i) glucosyl residues of glycogen are mo bilized after application of peroxides despite the presence of exogenous gl ucose, and (ii) that the demand for glucose-6-phosphate as substrate for NA DPH regeneration via the pentose phosphate pathway can, at least partially, be met by mobilization of glycogen. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.