Heavy metal detoxication in Mytilus kidney--an in vitro study of Cd- and Zn-binding to isolated tertiary lysosomes.

Uptake of Cd and Zn by isolated lipofuschin granules (tertiary lysosomes) has been studied. Freshly isolated granules contain Zn and approx 85% is immobilised. The granules take up ionic Cd and Zn from the surrounding medium. The metals are weakly and reversibly bound by a passive, non-concentrative adsorption process. Multiple, non metal-specific binding sites with a pKapp approximately equal to 6 and stability constant approximately equal to 5 were found. Metals can be sequestered from proteins with weakly bound metal but not from Cd-thionein. The results are discussed in relation to intracellular control of heavy metal concentrations in the cell and the pathway of Cd metabolism.