The response of lufenuron‐ And flonicamid‐exposed Cyprinus carpio to saltwater challenge: Study on ion‐regulation and stress genes expression and plasma antioxidant characteristics

Two groups of juvenile common carp (Cyprinus carpio) were exposed to sub-lethal concentrations of lufenuron (0.11 mg/L) and flonicamid (0.43 mg/L) for 21, followed by exposure to saltwater (12 g/L). The fish were sampled before saltwater exposure (i.e. after 21 days exposure to the pesticides) and 24, 72 and 120 hr after the saltwater challenge. Plasma antioxidant characteristics and the expression of gill osmoregulatory and stress genes were studied. The results showed that Na+/K+-ATPase gene expression of the lufenuron-exposed fish was higher than the flonicamid-exposed one. However, there were no significant differences in Na+/K+-ATPase gene expression between the pesticides-exposed fish and the control group. Both lufenuron and flonicamid increased the expression of cortisol receptor gene. Cortisol receptor expression increased 24 hr after the saltwater exposure and decreased afterwards. HSP70 gene expression of the pesticides-exposed fish showed no significant difference compared to the control group; however, the salinity challenge caused significant elevation in HSP70 gene expression at 72 and 120 hr. Plasma SOD activity of the flonicamid-exposed fish was significantly lower than the control fish, before the saltwater exposure; however, an inverse pattern was observed 24 hr after that. Compared to the control fish, plasma CAT activity and MDA levels increased in the pesticide-exposed fish after the saltwater exposure. In conclusion, exposure to lufenuron and flonicamid increased cortisol receptor gene expression, which indicates stress induction. Both pesticides induced oxidative stress, before and after the saltwater exposure.