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THERMOREGULATION IN THE RAT DURING CHRONIC, DIETARY EXPOSURE TO CHLORPYRIFOS, AN ORGANOPHOSPHATE INSECTICIDE.
Citation:
Gordon, C J., R. Marshall, D. Hunter, P Becker, AND B Padnos. THERMOREGULATION IN THE RAT DURING CHRONIC, DIETARY EXPOSURE TO CHLORPYRIFOS, AN ORGANOPHOSPHATE INSECTICIDE. Presented at Experimental Biology 2002, 4/24/2002, 4/20/2002.
Description:
Administration of chlorpyrifos (CHP) at a dose of 25 to 80 mg/kg (p.o.) To rats results in hypothermia followed by a fever lasting for several days. To understand if chronic, low level exposure to CHP affects thermoregulation in a comparable manner to acute administration, male Long-Evans rats were subjected to 0, 1, or 5 mg CHP/(kg day) in their diet for six months. Food consumption was limited such that body weight was maintained at 350 g throughout the study. After 4 months of treatment, core temperature (Tc) and motor activity (MA) were monitored by radio telemetry. CHP at 5 mg/(kg day) led to a 0.1 C increase in Tc. The rats were then administered a challenge dose of CHP (30 mg/kg, p.o) while Tc and MA were monitored by telemetry. Rats fed the 1 and 5 mg/kg CHP diets showed a significantly greater hypothermic response and reduction in MA following CHP challenge compared to controls. The results were confounded by a 180 shift in Tc and MA rhythms caused by the restricted feeding protocol. However, ad libitum feeding of CHP (7 mg/(kg day) led to a significant 0.1 to 0.2 C elevation in day time Tc but no change in MA. Overall, chronic exposure to relatively low doses of CHP leads to subtle elevations in Tc and sensitizes the rat's thermoregulatory response to acute CHP exposure. This abstract does not necessarily reflect U.S. EPA policy.