Impact on the Activity of Acetylcholinesterase(AChE)in Head and Bioconcentration in Zebrafish(Brachydanio rerio)After Chronic Exposure to Chlorpyrifos and Triazophos

The acetylcholinesterase(AChE)activities in zebrafish(Brachydanio rerio)head was studied after chronic exposure at sublethal concentrations(1/10, 1/20, 1/40 or 1/80 of 96 h-LC50)of chlorpyrifos and triazophos, and the bioconcentration of these pesticides in fish was investigated as well. The results showed that the AChE activity gradually reduced with increasing of the exposure time and concentrations. When the concentrations of the pesticides were 1/10 of 96 h-LC50 and exposed for 30 days, the activities of AChE in zebrafish head were 42.25% and 31.80% of control for chlorpyrifos and triazophos, respectively. The recovery activities of AChE by chlorpyrifos were all over 90% of control in all the treatments 30 days after the pesticide was removecd. However, the recovery activities of AChE inhibited by triazophos were 74.91% and 71.46% of control at the high concentration exposures(1/10 and 1/20 of 96 h-LC50). Chlorpyrifos could be easily taken up and concentrated by zebrafish from water, and the bioconcentration factors(BCF30 d)were 260.91~1 320.03 L·kg-1 after exposure of 30 days, while for triazophos ranged 8.23~26.84 L·kg-1.