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Preparations containing both organophosphates and pyrethroids are commonly used in insect control. Toxicokinetic interactions between α-Cypermethrin (CM ) and Chlorpyrifos (CPF) were studied in rats. The animals were given a solution of CM or CPF in rapeseed oil at a dose of 10 mg/kg and a mixture of CM and CPF at a dose of 5 mg/kg each by an intragastric tube once a day for 28 days. The concentrations of unchanged CM and CPF were determined in blood, liver and brain by GC-ECD. Also, the concentrations of CM and CPF were individually monitored in blood after administration of their single doses to calculate toxicokinetic parameters (Tmax., Cmax., AUC ). In urine the main metabolites 3-(4’-hydroxyphenoxy)benzoic acid (4OH3PBA) and 3,5,6-trichloro-2-pyridinol (TCP) were determined by HPLC in the rats treated daily with CM , CPF or their mixture. In the animals dosed with a single insecticide, the highest concentration of CM was found in blood and of CPF in liver. In the co-exposed rats, CPF decreased in all the tissues, while CM increased particularly in liver. The excretion of 4OH3PBA following CM administration increased significantly during the exposure period, whereas in the CPF-exposed rats, TCP was excreted at the same rate. Following the co-administration of both insecticides 4OH3PBA excretion decreased, but did not influence TCP excretion. In the coexposed animals, Cmax. and AUC increased for CM, and decreased for CPF.
In the current study the influence of single compounds and concurrent exposure to popular insecticides: organophosphate (OP) – chlorpyrifos (CPF) and synthetic pyrethroid (PYR ) – α-cypermethrin (CM) on some oxidative stress parameters and cholinesterase (ChE) activity in rats was investigated. Animals received by gavage 10 mg of single compounds or 5 mg of each per kg bw daily in rapeseed oil for 14 and 28 days. Concentrations of total thiols and TBARS, activity of catalase and cholinesterase were measured in tissues. Total thiol concentrations declined in plasma in all experimental groups after 14 and 28 days, while in liver a decrease was noted after only 14 days in animals receiving CPF and after 28 days in rats treated with CM alone with a mixture of pesticides. Lipid peroxidation presented as TBARS concentration was elevated mostly after 2 weeks of exposure in brain and liver but not in plasma in all experimental groups. Catalase activity increased in erythrocytes in all groups treated with insecticides, while in liver CM administered alone reduced the activity of the enzyme. Cholinesterase was markedly depressed to a different degree in plasma and brain of animals receiving CPF alone or in combination, while CM did not significantly elevate brain ChE. The results of this study seem to indicate that CM and CPF apart from known modes of action demonstrate their toxicity also through free radical mediated mechanisms. It is also evident that CM administered with CPF does not affect the cholinesterase inhibition generated by the latter.
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