Potential role of metal-binding proteins in cadmium detoxification in themisto libellula (mandt) and themisto abyssorum boeck from the greenland sea

Frequently reported high body concentrations of Cd (reaching 100 μg g−1; dry wt) in adult hyperiid amphipods of the genus Themisto from various temperate and polar marine waters suggest that these animals must have evolved efficient detoxification mechanisms. The potential role of metal-binding proteins in amphipods collected from the Greenland Sea was investigated by analysing subcellular metal distributions and by analysing the cytosolic fraction with the aid of gel chromatography. We find about 66% of the total Cd in pellets after centrifugation of homogenates. The remaining cytosolic Cd fraction (about 34%) is mainly related to proteins in the molecular mass range of 18 kDa and with some properties characteristic of metallothioneins. About 70–80% of these compounds belong to a heat-stable pool. The masses of these proteins recovered in the elutions are too low to permit further analytical characterisation. Thus, the nature of this cellular Cd sequestration is open to discussion.