Transport and storage of metals

Current understanding of the means by which the trace metals copper, iron, and zinc are transported and stored in the human body is reviewed. Although metal-related inherited metabolic diseases manifest themselves as deficiencies in metalloenzymes, these deficiencies in fact arise from disturbances in the absorption/rejection or transport or storage phases of the metal metabolism. The considerable information available on iron metabolism shows these phases to be closely interrelated with a number of feedback mechanisms operating as controls on the various metabolic stages. Copper and zinc have vastly different roles in their enzymes but, following their close coordination chemistry properties, have similar metabolic routes. Both make use of albumin for transport and of metallothionein at the absorption and hepatic-binding stages. In contrast to iron, copper and zinc have no well-defined storage system; instead they make use of body reserves distributed in various tissues. Our knowledge of the transport and storage systems of the trace metals is still very incomplete. More research is needed on the dynamics of movement of the trace metals between the various body tissues and fluids. Further advances will also come from the study of related metal inherited diseases in other animal species.