Alterations in Plasma and Tissue Acetylcholinesterase Activity Following Repeated Oral Exposure of Chlorpyrifos Alone and in Conjunction with Fluoride in Wistar Rats

Concurrent exposures of more than one environmental contaminants are commonly encountered by human beings and animals. This study investigated the effect of chlorpyrifos alone and in conjunction with fluoride on plasma and tissue acetylcholinesterase (AChE) activity in wistar rats. Fluoride at 1 or 10 ppm in drinking water produced significant (P < 0.05) inhibition of AChE activity in a dose dependant manner and inhibition was maximum in brain (26.39 %) and least in heart (10.23 %). Similarly repeated oral administration of chlorpyrifos at 1 or 10 mg/kg produced a significant dose dependant inhibition of AChE activity (P < 0.05) which was observed maximum in brain (28.93 %) and least in heart (12.86 %). Co-exposure of chlorpyrifos and fluoride at higher doses produces more pronounced inhibition as compared to chlorpyrifos or fluoride exposed groups. Co-exposure produces maximum inhibition in erythrocyte (37.54 %) and least in plasma (18.26 %) of exposed animals as compared to control group. Observations from the present study suggested that co-exposure of fluoride and chlorpyrifos produces more pronounced inhibition of AChE than the individual exposure of either toxicant. Therefore the applications of chlorpyrifos as a pesticide should be reduced in areas where fluoride level in soil or ground water is high to avoid AChE inhibition.