[Dependence of the rate of the pentose cycle reactions on the degree of glutathione reduction in erythrocytes].

The stationary dependence of the rate of pentose cycle in erythrocytes measured by CO2 production on the degree of glutathione reduction typical for the pentose cycle was established. The steady-state rate of oxidation from the physiological to maximal values was generated by the addition of tretbutylhydroperoxide, a substrate of the glutathione peroxidase reaction, to erythrocyte suspension at a constant rate. The steady-state rate of CO2 production was correlated with the rates of oxidant addition throughout the experiment. The parameters of the pentose cycle reactions under conditions when the maximal rate of the pentose cycle and glutathione pool (GSH+2 GSSG) are taken for 100%, coincided for all donors tested. The increase in the rate of pentose cycle from 0 to 60% of the maximal one had practically no effect on the concentration of GSH, which was as high as 90% of the overall glutathione pool, thus indicating a high stabilization degree of GSH (stabilization coefficient was about 15). A further increase of the rate up to maximal values resulted in a rapid fall of the GSH level down to 0. The data obtained support the previously described mathematical model for regulation of glutathione metabolism. The GSSG liberation from the erythrocytes was shown to be directly proportional to the stationary intracellular concentration of GSSG; the transport rate constant varied in different donors from 0.15 up to 0.6(-1). The increase of oxidation rates up to maximal values, when GSSG concentration was approximated to the glutathione pool leads to a reversible decrease of GSSG concentration, which destroys the steady-state equilibrium of the pentose cycle.