Effects of zinc exposure on the bioaccumulation of cadmium in the subcellular fractions of freshwater crab Sinopotamon henanense gills

To investigate the effects of zinc exposure on the bioaccumulation of cadmium in the gills of the freshwater crab,laboratory-reared Sinopotamon henanense were exposed to either cadmium alone or the combination of cadmium and zinc at different concentrations,and then were sampled at day 14 and day 28 after exposure. By using the subcellular fractionation method,the collected grills were separated into four parts,namely,the heat-stable protein( HSP),metal-rich granules( MRG),biologically active metals( BAM) and the cellular debris( CD). The HSP and MRG belong to biological detoxified metals( BDM). The cadmium accumulation in each part was measured by the flame atomic absorption spectrophotometry( AAS). The results demonstrated that BDM contained 50% of cadmium in all the parts,suggesting an important fraction for cadmium accumulation. Either high( 1000μg·L-1) or low( 100 μg·L-1) concentration of zinc promoted cadmium accumulation in the HSP and MRG at low exposure concentration of cadmium,while inhibiting its accumulation at high exposure concentration. In BAM,either high or low concentration zinc played promoting effects at certain degree on cadmium accumulation,while lower concentration of Zn showed better promoting performance than higher concentration of Zn. In summary,the results suggested that exposure to Zn affected the bioaccumulation and distribution of Cd in the gills of the freshwater crab Sinopotamon henanense.