Characterization of metal-containing granules from the kidney of the common mussel, Mytilus edulis

The metal-containing membrane-limited granules which make up some 20% of the cellular volume of the kidney cells of the marine mussel, Mytilus, have been purified and partially characterized by chemical and histochemical analysis. They contain an inorganic component (10% of their dry weight), principally iron, zinc and calcium, associated with sulphur phosphorus together with a pigmented organic component which has the histochemical and spectroscopic of lipofuschin. Microscopic and enzymic evidence indicates that the lipofuschin is present as a result of lysosomal degradation and peroxidation of cellular membranes. The granules may thus be regarded as tertiary lysosomes or residual bodies. The ash content of these lysosomes is 10-fold higher than those from mammalian sources. For this reason, Mytilus may be a useful model system for the study of intralysosomal metal accumulation.