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CHLORPYRIFOS AND 3,5,6 TRICHLORO-2-PYRIDINOL DISTRIBUTION IN RAT BLOOD AND BRAIN DURING CHRONIC DIETARY AND REPEATED HIGH LEVEL ACUTE EXPOSURE TO CHLORPYRIFOS.
Citation:
HUNTER, D. L., R. S. MARSHALL, E. REYNOLDS, AND S. J. PADILLA. CHLORPYRIFOS AND 3,5,6 TRICHLORO-2-PYRIDINOL DISTRIBUTION IN RAT BLOOD AND BRAIN DURING CHRONIC DIETARY AND REPEATED HIGH LEVEL ACUTE EXPOSURE TO CHLORPYRIFOS. Presented at Society of Toxicology, San Diego, CA, March 05 - 09, 2006.
Description:
The aim of this study was to determine the concentrations of an organophosphorus pesticide, chlorpyrifos (CPF), and the metabolite 3,5,6 trichloro-2-pyridinol (TCP) in tissues from rats exposed to long-term, low-dose CPF. Adult, Long-Evans male rats received CPF for one year at three levels of dietary exposure (0, 1, or 5 mg/kg/day); half of each group were also given a spike dose of CPF by oral gavage every 2 months and the other half received corn oil vehicle. Therefore, there were 6 treatment groups: 0+oil, 0+CPF, 1+oil, 1+CPF, 5+oil, and 5+CPF with an n=4-6 per group. Brain and blood were harvested after 6 and 12 months of the diet/spike regimen (24 hrs after the last spike) and 3 months after the cessation of treatment (recovery animals) and levels of CPF and TCP were assessed by HPLC. No CPF or TCP was found in the recovery animals. CPF was rarely noted in either brain (2%) or blood (8%) samples. TCP also was rarely detected in the brain (8%), but was present in many blood samples. Only 30% of the animals from the 1+oil group showed measurable blood TCP, but in the other treatment groups (0+CPF, 1+CPF, 5+oil, and 5+CPF) 100% of the animals had TCP in their blood. Durations of dosing did not alter blood TCP level: the 6 and 12 months time points were not different. As expected, blood TCP was approximately 8x higher in the animals receiving the spike dose of CPF compared to those receiving a vehicle spike. For either the CPF- or vehicle-spiked rats, blood TCP levels were higher in animals receiving the 5 mg/kg/day diet as compared to those receiving the 0 or 1 mg/kg/day CPF in the diet; however, there was no difference between those receiving control diet and the 1 mg/kg/day diet. Therefore, a chronic exposure to low level of CPF (1 mg/kg/day) did not alter the response to a CPF challenge as compared to animals receiving no CPF in their diet. This is an abstract of a proposed presentation and does not reflect Agency policy.