Concentration related differences in the inhibition of acetylcholinesterase activity in the common carp Cyprinus carpio by Phorate, an organophosphorous insecticide

Abstract

The activity of acetylcholinesterase (AChE) in the vital organs of fish such as gill, liver, muscle, kidney and brain of the freshwater common carp Cyprinus carpio ( C. carpio ) was investigated after exposing to acute lethal toxicity (ALT) and chronic sublethal toxicity (CST) of phorate. C. carpio fish were exposed to ALT (LC₅₀/96 hours - 0.71 ppm/l) of Phorate for one day and 4 days and CST (one-tenth of the LC₅₀/96 hours - 0.071 ppm/l) of Phorate for 1, 7, 15 and 30 days and the concentration related differences in the inhibition and recovery of the AChE enzyme activity was evaluated in the target organs of the fish. Relative to controls, the activity of AChE in all the organs of the fish exposed to ATP gradually decreased significantly ((P 0.05)) at 1 and 4 days of exposure period whereas in the fish exposed to CTP the AChE activity was elevated at day 1 and gradually decreased from day 7 to day 15 followed by an increase at day 30 in all the organs significantly (P 0.05). Based on the percent values obtained the inhibition of AChE activity was predominantly more in the organs of the fish exposed to ATP in a concentration-dependent manner. On prolonged exposure for 30 days in CTP the AChE activity was restored gradually depending on the initial pesticide exposure concentration. Findings from this study have demonstrated that inhibition of AChE activity in C. carpio is a useful biomarker for assessment of anticholinesterase pesticide contaminations in water.