Student Research: Travis Cook

MS, , 2009
Faculty Advisor: Christopher D. Simpson

Evaluation of Chlorpyrifos Protein Adducts in Rat Blood Plasma by Mass Spectrometry-Based Proteomics


Abstract

Organophosphorus pesticides (OPs), which are frequently used in agricultural settings, are able to effectively exterminate insects by inhibiting the enzyme acetylcholinesterase (AChE) at cholinergic nerve synapses. Overexposure to OP pesticides results in the same toxic action within the human body. The EPA has estimated that approximately 10,000 to 20,000 agricultural workers suffer such poisonings each year in the United States. In this study, the rat blood plasma proteome was analyzed for changes associated with exposure to the OP pesticide chlorpyrifos. Adult male Fischer F344 rats with surgically implanted jugular vein catheters were dosed with 10 mg/kg of chlorpyrifos by oral gavage. Blood samples were then collected in series via the jugular vein catheters at 1, 2, 4, 8, 24, 36, and 48 hours following the exposure. Aliquots of the rat blood plasma were prepared for mass spectrometry (MS) analysis by digestion with trypsin and desalting the samples, but high abundance proteins were not removed. The samples were analyzed utilizing high performance liquid chromatography – mass spectrometry (HPLC-MS) based proteomics. MS proteomics is a hypothesis generating method that can potentially identify indicators of disease and/or exposure. Using this methodology, it was hypothesized that protein adducts of chlorpyrifos would be able to be identified in the rat blood plasma. These adducts may be able to provide new insights into the mechanisms of chlorpyrifos toxicity and provide novel biomarkers of OP pesticide exposure in the blood plasma. It was found that the administered dose effectively inhibited plasma butyrylcholinesterase (BuChE), but no adducts were identified on the high abundance plasma proteins. It was thus concluded that although the delivered dose elicited a toxic response, novel biomarkers of exposure were unable to be identified by the experimental approach taken.