Use of hydroperoxides in the studies of glutathione metabolism in rat lens

t-Butyl hydroperoxide, a substrate for glutathione peroxidase, has been used to enzymatically oxidize lens GSH. t-Butyl hydroperoxide, 2 mm and 5 mm, oxidized almost 80% of lens GSH in vitro in 30 min and 8 min, respectively, at 25°. After treatment with 2 mmt-butyl hydroperoxide for 30 min, total GSH and GSSG in the lens could not account for about 50% of GSH present in the lens at 0 hr. However, incubation of these lenses, treated with t-butyl hydroperoxide, in the presence og glucose regenerated more than 80% of total glutathione in about one hour. This indicated that during oxidation with t-butyl hydroperoxide glutathione gets bound to proteins. A substantial amount of mixed disulfide of proteins and glutathione (protein-S-SG) is formed when GSH in the lens is oxidized with 5 mm-t-butyl hydroperoxide for 8 min. The mixed disulfide thus formed could be cleaved with glutathione reductase-NADPH system and by potassium borohydride to release GSH. However, a portion of protein-bound GSH as determined by the borohydride method could not be cleaved by the glutathione reductase-NADPH system. The glycolytic and shunt pathway enzymes of glucose metabolism were not affected by incubation of the lenses with 5 mm-t-butyl hydroperoxide for 8 min at 25°.