Abstract
Pyrethroids (cypermethrin and fenvalerate) have high pesticidal activity and low toxicity to non-target organisms. Organochlorines and, recently, organophosphates have been shown to produce oxidative stress through the generation of free oxygen radicals. However, there are no reports which show involvement of reactive oxygen species (ROS) in pyrethroid toxicity. The present study was undertaken to determine pyrethroid-induced lipid peroxidation (LPO) and to show whether pyrethroid intoxication alters the antioxidant system. Male Wistar rats weighing 150-180 g were administered a single dose of 0.001% LD50 cypermethrin and/or fenvalerate orally and the rats were sacrificed at 0, 1, 3, 7 and 14 days of treatment. Liver, kidney and heart tissues were removed and washed in phosphate buffered saline pH 7.4. The tissues were homogenized and samples were centrifuged to obtain cytosolic fraction. LPO, antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione (GSH) content were determined in the tissues at various time periods. The results showed increased LPO in tissues with recovery towards control within 14 days of treatment. SOD and CAT activity in tissues increased, probably in response to the generation of ROS. The depletion in GSH content and the decrease in GST activity in tissues may contribute to the increased LPO. Acetylcholinesterase (AChE) activity in tissues was inhibited in pyrethroid toxicity. The results show the involvement of ROS in pyrethroid toxicity as it increased LPO and altered the antioxidant system.