Tissue-specific cadmium and metallothionein levels in freshwater crab Sinopotamon henanense during acute exposure to waterborne cadmium.

The freshwater crabs Sinopotamon henanense were exposed to different concentrations of waterborne cadmium (Cd). The relationship between tissue-specific Cd accumulation and metallothionein (MT) induction was investigated using the Cd saturation assay and atomic absorption spectrophotometry method. The results showed that Cd accumulation rose significantly in all tissues studied after Cd exposure, and the Cd accumulation level in various tissues followed the following order: gill > hepatopancreas > muscle > ovary. MT levels were clearly tissue-specific after Cd exposure. Hepatopancreas was found to have the highest MT level, followed by the gill, muscle, and ovary. In conclusion, the results indicated although Cd exposure clearly resulted in MT induction, its synthesis does not correlate with Cd accumulation in the later stage of Cd exposure. The calculated ratios of actual Cd to theoretical maximum Cd-MT in the hepatopancreas were <1.0 under acute waterborne Cd at all sampling points, indicating that the hepatopancreas had much greater Cd-binding potential of MT than the gill, muscle, or ovary. It is clear from our results that a positive correlation was shown between MT induction and Cd accumulation both in hepatopancreas and gill. Therefore, MT induction can be considered as a biomarker for acute waterborne Cd pollution.