Effects of atrazine and chlorpyrifos on the production of nitric oxide and expression of inducible nitric oxide synthase in the brain of common carp (Cyprinus carpio L.)

• NO and iNOS were investigated exposed to ATR, CPF and their mixture.
• ATR, CPF and their mixture increase production of NO and iNOS activity.
• ATR and CPF can up-regulate iNOS expression in the brain of common carp.

The study aimed to investigate the effects of atrazine (ATR), chlorpyrifos (CPF), and the mixture of them on nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in the brain of common carp. The triazine herbicide ATR and the organophosphorus insecticide CPF are frequently and extensively applied in agriculture all over the world. 220 Carps were averagely divided into eleven groups according to the different treatments and concentration, including the exposure and recovery experiments. In the present study, we investigated production of NO, iNOS activity and iNOS mRNA and protein expression in the brain of the common carp after a 40 d exposure to ATR, CPF, alone or in combination, and a 40 d recovery treatment. The results showed that the activity of iNOS and production of NO were significantly higher in all groups of fish exposed to high doses ATR, CPF and their mixture compared to control fish. After a 40 d recovery treatment, iNOS activity and production of NO were lower than in the corresponding exposure groups in all the recovery groups. The mRNA and protein levels of iNOS were significantly higher in the high-dose group of ATR and CPF compared to control group, but were significantly lower in the group of the mixture of ATR and CPF compared to control group. Results indicated that NO and iNOS were involved in oxidative stress and brain tissue damage induced by ATR, CPF, and their mixture. Thus, the information presented in this study is helpful to understand the mechanism of ATR-, CPF- and ATR/CPF-mixture-induced neurotoxicity in fish.