Effect of organophosphorus pesticide Chlorpyrifos on thyroid hormone changes in grass carp (Ctenopharyngodon idellus)

Document Type : Research Paper


1 Scientific Member in Department of Biology, Faculty of Sciences, Payame Noor University, Oshnaviye, Iran

2 Assistant Professor in Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Iran.


Chlorpyrifos is one of the strong organophosphate pesticides that is used elaborately which cause poisoning, disrupting immune and physiological systems affecting vital activities of fishes. Therefore, its effects can be used as the biological indicators for pollutants. In this study, the effect of different concentrations of Chlorpyrifos (5, 10, 20, 30 and 40 mg/L) were investigated on thyroid hormone levels in grass carp (Ctenopharyngodon idellus) during 14 days of experiment. Blood sampling was performed in 12, 24 and 96h and also 7 and 14 days after the exposure. The concentrations of serum thyroid hormone were determined using Radioimmunoassay method. Results showed the significant decrement in the serum T3 and increment of the serum T4 in the treated fishes in comparison to the control groups. In addition, the decrement in ratio T3/T4 was observed (P<0.05). In conclusion, the Chlorpyrifoswas classified as an intense toxic pesticide for the grass carp that have high effects on the fish thyroid hormones equilibrium, metabolism activity, and growth.