The response of antioxidant and atpase enzyme systems response against single cadmium, binary effects of imidacloprid and cadmium in daphnia magna

The present study aimed to evaluate the oxidative stress and osmoregulatory system damage-inducing potential of binary mixtures of neonicotinoid insecticide imidacloprid (IMI) and cadmium (Cd2+) in Daphnia magna. Animals were exposed to subchronic effects (7 days) of IMI and Cd2+ with single and binary mixtures. ATPase (Mg2+-, Na+, K+-, and Ca2+-ATPase) and antioxidant enzymes (catalase, CAT; superoxide dismutase, SOD, and glutathione peroxidase, GPX) activities with lipid peroxidation (thiobarbituric acid reactive substances, TBARS) and protein levels were measured spectrophotometrically. While the enzyme activity changes showed a decreasing trend upon the single effect of IMI exposure, there was an increasing trend after the Cd2+ effect. Nevertheless, the combined effects of IMI and Cd2+ did not show a clear response pattern dependent on IMI dose, except for the increase in lipid peroxidation. Ca2+-ATPase and CAT were observed to be the most sensitive biomarkers in the toxicity response. However, the decrease in protein levels except the low IMI exposed group indicated an energy requirement in D. magna due to oxidative stress. IMI and Cd2+ toxicity caused damage to the antioxidant and osmoregulatory system due to their oxidative potential on cellular targets (biomarkers), despite variations in their single and combined effects. The current data emphasized that investigating the combined effects of toxic compounds at their environmental level based on the multi-biomarker approach is essential in the realistic evaluation of toxicity in toxicological research. Keywords: ATPase, Cadmium, Daphnia, Imidacloprid, Oxidative stress