Correlation between glutathione and stimulation of the pentose phosphate cycle in situ in Chinese hamster ovary cells exposed to hydrogen peroxide

The effect of glutathione on stimulation of pentose phosphate cycle activity during oxidative challenge was evaluated in intact Chinese hamster ovary cells in situ. Glutathione was depleted to varying levels with L-buthionine-[S,R] sulfoximine. The level of stimulation of pentose phosphate cycle activity by exogenous H2O2 (4 mumol/10(7) cells) was dependent on the time of pretreatment with L-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 H2O2 stimulated pentose phosphate cycle activity. The amount of GSSG in cells increased after exposure to 10-fold higher concentrations of H2O2 under 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 of L-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 of L-buthionine-[S,R] sulfoximine on stimulation of pentose phosphate cycle activity by H2O2 did 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.