Analysis of cholinesterases activity and their variation in rat serum upon repeated exposure to chlorpyrifos

Objective To study activity of acetylcholinesterase(AChE)and butyrylcholinesterase(BuChE)in rat serum at different time points after repeated exposure to chlorpyrifos(CPF);to analyze relationship of the activity of AChE and BuChE. Methods 60female adult SD rats were randomly divided into 5groups by weight,12rats in each group:4chlorpyrifos dose groups(dosage:2.50、5.00、10.00、20.00mg/kg)and 1control group.Rats in all groups were successively treated with CPF for 10days by gavage.Blood samples of 3rats in each group were collected at 2nd,4th,7th and 11th d,activity of AChE and BuChE was determined.Results Serum AChE and BuChE activity decreased upon prolonged exposure time or when chlorpyrifos dosage increased in a dose-dependent manner.Activity of AChE and BuChE in serum showed a positive correlation(r= 0.872,P0.01),with similar trend upon repeated exposure.However,BuChE demonstrated greater inhibition effect compared to AChE(P0.01).Conclusion Inhibition of AChE and BuChE increased upon 10drepeated exposure to CPF.Serum BuChE can be considered as a sensitive indicator for organophosphorus pesticide exposure.