Abstract
The activities of glutathione-related enzymes in isolated rat small intestine were investigated under oxidative stress mediated by Fe2+-EDTA. The isoelectric points and approximate molecular weights of the enzymes investigated were first determined. The reduced and oxidized glutathione contents, and low molecular weight thiols in isolated rat small intestine were also studied under oxidative stress. Significant reducing activities of glutathione S-transferase and lactate dehydrogenase were observed accompanied by increases in oxidized glutathione content, whereas thioltransferase, glutathione reductase, glutathione peroxidase and thioredoxin reductase retained the same levels of activity as controls. First-order inactivation of purified rat small intestime glutathione S-transferase including class-α, μ and π was observed and the isozyme class-π was inactivated at several pH's under Fe2+-EDTA-mediated oxidative stress. Leakage of protein and both reduced and oxidized forms of glutathione was significantly increased during incubation with Fe2+-EDTA. In conclusion, enzymes which were not inactivated under Fe2+-EDTA-mediated oxidative stress may play an important role in cellular antioxidant defenses in the small intestine. Furthermore, enzymes such as glutathione S-transferase, mainly a class-π isozyme, and lactate dehydrogenase which were inactivated may form part of the barrier against oxidative stress similar to reduced glutathione.
