Effects of dibutyl phthalate and di-ethylhexyl phthalate on acetylcholinesterase activity in bagrid catfish, Pseudobagrus fulvidraco (Richardson)

Acetylcholinesterase (AChE) activity is a well-known biomarker for exposure to organophosphate or carbamate compounds in aquatic organisms. However, the effect of dibutyl phthalate (DBP) and di-ethylhexyl phthalate (DEHP), widely used as a plasticizer, on the change of AChE activity is not yet known. Bagrid catfish Pseudobagrus fulvidraco were administrated with 100, 500 and 1000 mg kg⁻¹ diet of DBP or DEHP and the effects on AChE activity were assessed in the liver, gill, kidney, heart, brain, muscle and eye of the exposed fish. All tissues contained different background AChE activity in non-treated bagrid catfish: the highest was observed in the brain, followed by muscle, heart, and kidney. The enzyme activities in various tissues were significantly inhibited after exposure to DBP or DEHP in a concentration-dependent manner, especially in brain and muscle. A similar, but less pronounced, inhibition was also observed in liver and kidney when exposed to DBP and DEHP. Although AChE activity in gill and heart was also affected by DBP and DEHP, the decrease in these organs was least marked in these organs. Exposure to 1000 mg kg⁻¹ led to mortalities of 8.0% with DBH and 14% with DEHP; both seemed to be ascribable to phthalate toxicity. This study is the first report that the measurement of AChE activity in bagrid catfish is a valuable biomarker of DBP and DEHP exposure. This biomarker could be incorporated into a battery of biomarkers to strengthen the confidence with which ecotoxicologists can assess the impact of phthalate ester pollution in the aquatic environment.