The glutathione system of peroxide detoxification is less efficient in neurons than in astroglial cells

The ability of neurons to detoxify exogenously applied peroxides was analyz ed using neuron-rich primary cultures derived from embryonic rat brain. Inc ubation of neurons with H2O2 at an initial concentration of 100 mu M (300 n mol/3 ml) led to a decrease in the concentration of the peroxide, which dep ended strongly on the seeding density of the neurons. When 3 x 10(6) viable cells were seeded per dish, the half-time for the clearance by neurons of H2O2 from the incubation buffer was 15.1 min. Immediately after application of 100 mu M H2O2 to neurons, glutathione was quickly oxidized. After incub ation for 2.5 min, GSSG accounted for 48% of the total glutathione. Subsequ ent removal of H2O2 caused an almost complete regeneration of the original ratio of GSH to GSSG within 2.5 min. Compared with confluent astroglial cul tures, neuron-rich cultures cleared H2O2 more slowly from the incubation bu ffer. However, if the differences in protein content were taken into consid eration, the ability of the cells to dispose of H2O2 was identical in the t wo culture types. The clearance rate by neurons for H2O2 was strongly reduc ed in the presence of the catalase inhibitor 3-aminotriazol, a situation co ntrasting with that in astroglial cultures. This indicates that for the rap id clearance of H2O2 by neurons, both glutathione peroxidase and catalase a re essential and that the glutathione system cannot functionally compensate for the loss of the catalase reaction. In addition, the protein-normalized ability of neuronal cultures to detoxify exogenous cumene hydroperoxide, a n alkyl hydroperoxide that is reduced exclusively via the glutathione syste m, was lower than that of astroglial cells by a factor of 3. These results demonstrate that the glutathione system of peroxide detoxification in neuro ns is less efficient than that of astroglial cells.