Ecotoxicological effects of a veterinary food additive, copper sulphate, on antioxidant enzymes and mRNA expression in earthworms

• The oxidant effect of the contaminant copper sulphate on earthworms was investigated.
• Antioxidant enyzmes were applied as potential biomarkers.
• mRNA expressions of MT and Hsp70 genes as molecular tools were monitored.

The present study was aimed to investigate the effect of the veterinary food additive copper sulphate (CuSO4) on the eco-toxicological responses of earthworms Eisenia fetida (E. fetida). The following biomarkers were measured: catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) activities. Gene expression analyses such as metallothionein (MT) and heat shock protein 70 (Hsp70) were also examined. A time-dependent increase of CAT activity was found at 400 mg/kg and SOD activity at 200 and 400 mg/kg. The highest expression of Hsp70 (4.4-fold) was observed at day 15 at 400 mg/kg. Our results indicated that the measured antioxidant enzymes (except GST) had the ability to provide antioxidant defenses against the stressor; and compared to expression of MT, expression of Hsp70 could be more reliable molecular tools with predictive possibilities to monitor the eco-toxicity of stressors such as feed additive CuSO4.