Correlation between Glutathione and Stimulation of the Pentose Phosphate Cyclein Situin Chinese Hamster Ovary Cells Exposed to Hydrogen Peroxide

Abstract

The effect of glutathione on stimulation of pentose phosphate cycle activity during oxidative challenge was evaluated in intact Chinese hamster ovary cellsin situ.Glutathione was depleted to varying levels withL-buthionine-[S,R] sulfoximine. The level of stimulation of pentose phosphate cycle activity by exogenous H2O2(4 μmol/107cells) was dependent on the time of pretreatment withL-buthionine-[S,R] sulfoximine and was proportional to the total glutathione concentration. This was not related to the amount of GSSG, since its level was exceedingly low under conditions where H2O2stimulated pentose phosphate cycle activity. The amount of GSSG in cells increased after exposure to 10-fold higher concentrations of H2O2under conditions where there was no stimulation of pentose phosphate cycle activity above the basal level. Paraquat caused stimulation of pentose phosphate cycle activity which was independent ofL-buthionine-[S,R] sulfoximine pretreatment and of the glutathione content of cells. The stimulatory effects of both oxidants on pentose phosphate cycle activity appeared to be independent of glutathione reductase activity since they were unaffected in cells treated with 1,3-bis(2-chloroethyl)-1-nitrosourea. The inhibitory effect ofL-buthionine-[S,R] sulfoximine on stimulation of pentose phosphate cycle activity by H2O2did not appear to be due to the inhibitor itself, but rather to the overall level of glutathione. Glutathione could have a role in maintaining activity of the pentose phosphate cycle at a level which is appropriate for the severity of the oxidative challenge as well as for the capacity of the cellular antioxidant defenses.