Sulfoxaflor, Zn and their combinations disrupt the antioxidant and osmoregulatory (Ca-ATPase) system in Daphnia magna.

BACKGROUND

The oxidative- and osmoregulatory stress-inducing potential of binary mixtures of sulfoxaflor (SUL), a recently developed sulfoximine insecticide, and Zn was aimed to evaluate in Daphnia magna with different exposure regimes.

METHODS

Animals were exposed to different SUL concentrations (1.25, 2.5, 10, and 25 mg/L) for 7 days. In vivo 48 h and in vitro effects of single and binary mixtures of SUL (25 and 50 mg/L) and Zn (40 µg/L) were also determined. Furthermore, Ca-ATPase, oxidative stress biomarkers (catalase, CAT; superoxide dismutase, SOD; glutathione peroxidase, GPX; glutathione S-transferase, GST; reduced glutathione, GSH; thiobarbituric acid reactive substances, TBARS), and morphometric characteristics were measured.

RESULTS

Variable response patterns were observed due to exposure duration and regime, toxicant type, and concentration. Marked effects of SUL were observed, especially in subacute exposure, and 25 mg/L SUL concentration can be considered as a threshold level. Stimulation of GST activity was the most typical response, followed by declined SOD activity and GSH levels. GPX activity and TBARS levels responded differently depending upon the exposure type. Subacute and in vitro effects of SUL and Zn produced similar responses except for some cases. Ca-ATPase activity was altered differently upon subchronic duration, though inhibited by in vitro SUL+Zn effect. Subchronic SUL exposure increased body weight and length up to 25 mg/L, contrary to the observed decrease at higher concentrations.

CONCLUSIONS

Single and binary mixtures of SUL and Zn caused damage to the antioxidant and osmoregulatory system due to their oxidative potential on cellular targets (biomarkers). The current data emphasized that investigating the SUL toxicity with the Zn combination based on the multi-biomarker approach is essential in the realistic evaluation of SUL toxicity in toxicological research.