Enzymatic biomarkers of earthworms Eisenia fetida in response to individual and combined cadmium and pyrene

The responses of enzymatic biomarkers of earthworms Eisenia fetida to low-level exposures of cadmium (Cd) (2.50 mg kg−1), pyrene (0.96 mg kg−1) or their combination were investigated in this study. A set of enzymatic biomarkers, namely, cytochrome P450 (CYP) as a family of phase I enzymes, glutathione-s-transferase (GST) as one of phase II enzymes and antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT) ), was selected to evaluate the responses of the earthworms in a period upto eight weeks. The earthworms exposed to the mixture of Cd and pyrene demonstrated different responses of the enzymatic biomarkers from those exposed to Cd or pyrene alone. The responses of enzymatic biomarkers to the combined exposure were time-dependent, with initial antagonistic effects on CYP content and activities of GST and SOD, but with additive effects at the end of experiment causing the reductions of CYP content and GST activity and the enhancement of activities of SOD and CAT. Our results indicated the toxicity of low-level pyrene may be prolonged by the co-presence of Cd.

► This paper investigate toxic effects employing biomarkers on earthworms exposed to cadmium, pyrene and their mixture.
► The response of the enzymatic biomarkers of worms exposed to the mixture were different from those bare to Cd or pyrene alone.
► Cd co-presence increased the toxic effects of pyrene on earthworms.
► An antagonistic interaction of individual contaminants was observed initially and an additive contact at the end of trial.