Response of Oxidative Stress and Neurotoxicity Biomarkers in Rainbow Trout (Oncorhynchus Mykiss) After Exposure to Six-Metal Mixtures

Abstract The activity of liver catalase (CAT) and brain acetylcholinesterase (AChE) was assessed in rainbow trout (Oncorhynchus mykiss) after 7- and 14-day exposure to a six-metal mixture at the maximum permissible concentrations (MPC) accepted for inland waters in the EU (2013/39/EB; 2008/105/EB) (Zn – 0.1, Ni – 0.034, Cu – 0.01, Cr – 0.01, Cd – 0.0015 and Pb – 0.014 mg L-1) (Mix) and to the same six-metal mixtures with tenfold reduced concentration of Cu (Mix Cu↓) and Cr (Mix Cr↓) ions. A statistically significant increase of up to 26% of CAT and 52% of AChE activity was observed in rainbow trout after 7 days of exposure to the six-metal mixture at MPC in comparison to a control group. After 14 days of treatment, neither CAT nor AChE showed a significant response. Moreover, 7 and 14 days of exposure to the six-metal mixtures with the tenfold reduced concentrations of Cr or Cu ions did not significantly alter CAT activity. The six-metal mixture with the tenfold reduced concentration of Cr increased brain AChE activity in O. mykiss after 7 days of exposure (35%), but did not show a significant response in AChE activity in comparison to a control group after 14 days of treatment. After 7 and 14 days of exposure to the six-metal mixture with the tenfold reduced concentration of Cu ions, AChE activity did not vary significantly in comparison to control groups. Enhancement of catalase activity caused by the mixture of the six metals at MPC and the increased AChE activity in response to the same metal mixture and mixture with tenfold reduced Cr concentration after 7 days of exposure indicates the induction of oxidative stress and disturbance of cholinergic system homeostasis respectively.