Combined effects of oxytetracycline and Pb on earthworm Eisenia fetida

• The first to study combined effects of oxytetracyline and Pb on earthworm Eisenia fetida.
• Lysosomal membrane stability and cell apoptosis are more sensitive biomarkers to evaluate chemicals of lower toxicity and concentration.
• Joint toxicity decreased with increasing of OTC concentration, indicating an antagonistic effect.

Combined effects of oxytetracycline (OTC) and Pb on lysosomal membrane stability and coelomocyte apoptosis of earthworm were studied in the paper. Compared with control, the lysosomal membrane stability decreased and coelomocyte apoptosis increased in the treatments of single OTC and Pb contamination. As for compound pollution, combined effect of (5 mg/kg OTC + 50 mg/kg Pb) treatment on earthworm lysosomal was synergistic (except 28 d). However, it was antagonistic at higher concentration of (10 mg/kg OTC + 50 mg/kg Pb) and (20 mg/kg OTC + 50 mg/kg Pb) treatment. In addition, coelomocyte apoptosis of earthworm decreased significantly compared with single OTC, indicating an antagonistic reaction. And joint toxicity of OTC and Pb decreased significantly with the increasing OTC concentration.