Cadmium and the phosphate granules in Littorina littorea

Previous studies with the marine gastropod Littorina littorea have shown that cadmium is concentrated in the digestive gland and that cytosolic metallothionein-like proteins sequester a large proportion of the accumulated burden. In the current investigation, an electron microscope cryo-preparation method and X-ray microanalysis have revealed that some cadmium, in association with sulphur, is localised in the region of the limiting membrane of the mineralised granules which detoxify certain metals as an insoluble phosphate salt. It appears, therefore, that there could be interaction between the sulphur and phosphate systems for binding metals within the basophil cells of the digestive epithelium.