Protection from oxidant injury by sodium-dependent GSH uptake in retinal Muller cells

Glutathione (GSH) is known to play an important role in regulating oxidativ e damage to cells. The present study was initiated to examine the effect of exogenous GSH on oxidative injury in a retinal Muller cell line and to cha racterize GSH transport in these cells. Rat Muller cells (rMC-1) were incub ated with varying concentrations of t-butylhydroperoxide (t-BHP) to induce oxidative stress, and cell viability was measured after addition of GSH. In other studies, kinetics of GSH uptake and Na+-dependency were examined by incubating cells with S-35-GSH in Na+-containing and Na+-free buffers. GSH uptake was studied with GSH at concentrations varying from 0.05-10 mM in Na Cl buffer. In the presence of sodium, extracellular GSH provided protection against t-BHP-induced oxidant injury to rMC-1 cells; in contrast, the amin o acid precursors of GSH did not have any effect on cell viability. GSH was taken up by rMC-1 cells in a concentration- and sodium-dependent manner. K inetic studies revealed both a high affinity (K-m similar to 0.31 mM) and l ow affinity K-m (similar to 4.2 mM) component. Furthermore, GSH depletion h ad no significant effect on the rate of GSH uptake. The results show that p hysiological concentrations of GSH can protect Muller cells from oxidative injury. Both Na+-dependent and Na+-independent transport systems for GSH ex ist in Muller cells, and the Na+-dependent GSH transporter may be involved in the protective role of GSH. (C) 1999 Academic Press.