Abstract
Toxicosis due to paraquat, a redox cycling xenobiotic, is still a subject of much debate. In the present study on lipid peroxidation, paraquat had a biphasic effect on the malondialdehyde (MDA) level in rat liver microsomes; stimulation at the initial stage (within 10 min) and depression at the later stage. Although paraquat increased the initial rate of NADPH oxidation dose-dependently, the rate was not necessarily parallel with the increase in the MDA level. The MDA level increased linearly up to 0.1 mM paraquat added, but then it attained a plateau. The stimulation obtained by paraquat within 10 min was absolutely dependent on exogenous Fe2+ ion and NADPH, and the stimulation was entirely SOD sensitive, while the irondriven increase in MDA was 20% sensitive. Thus, there were different mechanisms between iron-driven lipid peroxidation and paraquat-modified peroxidation. Catalase increased the level, but mannnitol, a scavenger of OH, had no effect. EPR spectra showed that superoxide was formed dose-dependently up to 0.1 mM paraquat and that it attained a plateau at the same as MDA level described above. From these results, we concluded that paraquat stimulates lipid peroxidation through a mechanism dependent on the superoxide complex involving Fe2+ ion.
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Tomita, M., Okuyama, T. Effect of paraquat on the malondialdehyde level in rat liver microsomes (in vitro). Arch Toxicol 68, 187–192 (1994). https://doi.org/10.1007/s002040050053
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DOI: https://doi.org/10.1007/s002040050053