Biomarkers and bioaccumulation of clam Ruditapes philippinarum in response to combined cadmium and benzo[α]pyrene exposure

Biochemical and molecular biomarkers (the contents of metallothionein (MT), glutathione (GSH), the activities of aryl hydrocarbon hydroxylase (AHH), glutathione S-transferase (GST) and superoxide dismutase (SOD) and the mRNA expressions of GST-pi and Cu, Zn-SOD) were evaluated in clams Ruditapes philippinarum exposed to cadmium (Cd, 15 μg/L) and benzo[α]pyrene (BaP, 0.01 μg/L) individually and in combination (15 μg/L Cd + 0.01 μg/L BaP) for 21 days. The accumulation of Cd, BaP and the biomarkers measured in the gills and digestive glands of the clam showed significant increase in combination treatment and it was significantly higher than the Cd or BaP treatment (P > 0.05). The contents of MT increased in Cd and Cd + BaP treatment, while AHH activities were increased in Bap and Cd + BaP treatment (P > 0.05). GSH levels enhanced in Cd group and declined significantly in Cd + BaP treatment (P > 0.05). The activities of GST, SOD, and mRNA expressions of GST-pi, Cu, Zn-SOD increased remarkably in the clams exposed to combined pollutants. In this study, a significant interaction was observed for Cd and BaP accumulation in the clam and the current findings demonstrate the differences in antioxidant response of the biomarkers in clam to single contaminant and the mixtures.