Histochemical characterization of silver-induced metallothionein in rat kidney

Histochemical characterizations of Ag-induced metallothionein (MT) in the kidney of the rat have been reported. Ag, Cu and Zn contents increased in kidney and liver after Ag injection. In particular, the Cu content in kidneys increased dramatically after three injections of Ag. Sephadex G-75 elution profiles of the renal cytosol of rats injected with Ag revealed that the accumulated Cu in the kidney was bound to MT as were Ag and Zn. In addition, localization of Cu- and Ag-MT in the kidney was studied using autofluorescent signals, which are dependent on Cu- or Ag-thiol clusters, and immunohistochemistry. Although the MT induced by Ag was predominantly observed in the cortex of the kidney, some MT signals were also detected in the outer stripe of the outer medulla, as well as in the kidneys of LEC rats, an animal model of Wilson disease (a hereditary disorder of Cu metabolism). In these LEC rats, the Cu-MT also accumulated in the outer stripe of the outer medulla of the kidney. From these results, one possibility could explain that the Cu-MT detected in the outer stripe of the outer medulla in the kidney of Ag-injected rat was associated with the Cu transporter affected by Ag.