Water pollutants have a high potential risk for the population health. Protection from toxic impacts of water contaminants includes understanding the mechanism of low level toxicity and possible biological effect on people's health. Cd is one kind of conventional water contaminants which necessary to assess their potential negative effects. Zebrefish (Danio rerio)is often used as animal model in bioassessment. In this study, the fish was respectively exposed to 1/15 th (0.636 mg L -1 ), 1/10 th

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... (0.954 mg L -1 )and 1/5 th (1.908 mg L -1 ) of the LC 50 value, and the treatment was set for 5, 10, 15, 20 and 25 days. A decrease in biomarkers of AChE activity with dose and time-dependent manner and significantly increased in activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) in the brain and muscle of the fish when exposure to Cd. Then, the treatment was reduced the amount of protein content. This indicates that sublethal concentration treatment of Cd can cause changes at various levels, such as inducing alterations in the enzyme engaging in the control of cholinergic transmission, arising antioxidant competence and reducing protein content of the different tissues, which suggests low-level Cd contaminant may bring serious potential health risk.