Chlorpyrifos (CPF), commercially known as Dursban, is a broad-spectrum organophosphate insecticide that has been very widely used in the US as well as other countries to control both agricultural and residential pests. It is primarily a neurotoxic compound that, like other organo-phosphorothioates, is metabolized in vivo to CPF-oxon, which causes neurotoxicity via inhibition of acetylcholinesterase (AChE) at the cholinergic sites of the nervous system. The metabolic bio-transformation of CPF occurs predominantly by two pathways involving various cytochrome P450 (CYP) isoenzymes and a variety of esterases. The CYPs desulfurate CPF to corresponding toxic oxon while the esterases hydrolyze CPF and CPF-oxon to nontoxic products. Therefore, the degree of AChE inhibition and resultant toxicity of CPF is dependent on the production of active CPF-oxon as well as its deactivation by detoxifying enzymes. This brief review on the metabolism and toxicity of CPF is intended to highlight recent advances in research on the P450-mediated bioactivation of CPF and associated factors that may increase or decrease the CPF toxicity.
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