Laboratory bioassays on the response of honey bee ( Apis mellifera L.) glutathione S -transferase and acetylcholinesterase to the oral exposure to copper, cadmium, and lead

Abstract

In the present study, the influence of cadmium, copper, and lead on two enzymes often used as biomarkers in toxicological analysis was investigated. Bees were fed with 1 M sucrose solution containing 10-fold serial dilutions of CuCl₂ (1000 mg L⁻¹, 100 mg L⁻¹, and 10 mg L⁻¹), CdCl₂ (0.1 mg L⁻¹, 0.01 mg L⁻¹, and 0.001 mg L⁻¹), or PbCl₂ (10 mg L⁻¹, 1 mg L⁻¹, and 0.1 mg L⁻¹) during 48 h. Our results showed that the total glutathione S-transferase activity was not changed under the influence of cadmium and lead, and it was decreased with the highest concentration of copper. The level of gene expression of the three analyzed classes of glutathione S-transferase was significantly increased with increasing concentrations of copper and cadmium. Lead did not cause significant changes in glutathione S-transferase activity and gene expression, while it showed biphasic effect on acetylcholinesterase activity: lower concentration of lead, 0.1 mg L⁻¹ inhibited and higher dose, 10 mg L⁻¹ induced acetylcholinesterase activity in honey bees. Furthermore, our results showed a significant decrease of the acetylcholinesterase activity in honey bees treated with 0.001 and 0.01 mg L⁻¹ CdCl₂. Our results indicate the influence of cadmium, copper, and lead on GST and AChE in the honey bees. These results form the basis for future research on the impact of metallic trace element pollution on honey bees.

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