Lasting effect of preceding culture conditions on the susceptibility of C6 cells to peroxide-induced oxidative stress.

The aim of the present study was to investigate the influence of the maintenance culture conditions on the competence of C6 rat glioma cells to cope with peroxide-induced oxidative stress. C6 cells were maintained either in Ham's nutrient mixture F-10 supplemented with 15% horse serum and 2.5% foetal bovine serum (FBS) or in Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 5% FBS. The differently cultured cells were exposed under identical conditions to hydrogen peroxide (H₂O₂) and cumene hydroperoxide (CHP) in serum-free DMEM. The cells maintained in high serum Ham's F-10 medium (1) were less sensitive towards the cytotoxic action of both peroxides (EC₅₀-values: H₂O₂: 193 ± 23 μM; CHP: 94 ± 16 μM) than the cells maintained in low serum DMEM (EC₅₀-values: H₂O₂: 51 ± 10 μM; CHP: 27 ± 11 μM), (2) eliminated the peroxides (initial concentration: 100 μM) with higher rates (H₂O₂: 56 ± 5.5 vs. 32 ± 2.7, CHP: 32 ± 6 vs. 3.4 ± 0.6 nmol/min mg protein), (3) contained more glutathione (30 ± 2.5 vs. 14 ± 1.1 nmol/mg protein) and (4) owned a higher glutathione peroxidase activity (28 ± 3.4 vs. 9.5 ± 0.8 mU/mg protein). Glutathione reductase and catalase activities were not affected. These results demonstrate that the preceding culture conditions have a lasting effect on the susceptibility of cultured cells to oxidative stressors like peroxides. As cause for these differences a dissimilar supply of the cells with serum born antioxidants like selenium and α-tocopherol is discussed.