Effects of combined polystyrene microplastics and chlorpyrifos pesticide on enzymatic activities of different tissues in rainbow trout (Oncorhynchus mykiss)

Microplastics (MPs), mainly smaller than 5 mm, are vectors for various chemical compounds in the environment, such as pesticides and pollutants. Rainbow trout (Oncorhynchus mykiss) were exposed to two concentrations of chlorpyrifos (CPF; 2 and 6 μg/L), polystyrene microplastics (PS-MPs; 30 and 300 μg/L), and their combination. Significant changes were observed in the activities of catalase (CAT) and glutathione peroxidase (GPx) in mixed MPs and pesticide treatments. Microplastics increased the bioavailability of pesticides in kidney tissue samples for glutathione peroxidase (GPx) and catalase (CAT) enzymes. The activity of glutathione S-transferase (GST) in the liver showed a significant (p<0.05) increase between the treatments of 30 and 300 μg/L MPs compared to the control group. However, for GPx and CAT enzymes in the kidney showed increased activity compared to MPs and pesticide treatments. In conclusion, a mixed concentration of MPs and CPF showed significant effects on CAT, GPx, and GST activities in different tissue samples of O. mykiss.