Metallothionein and glutathione as determinants of cellular retention and extrusion of cadmium and mercury.

This work explored cellular trapping and extrusion of Cd and Hg in epithelial cells, with special emphasis on the jejunal mucosa. Important determinants of these processes are the concentration, diffusibility and relative metal affinities of a variety of cellular metal-binding compounds including metallothionein (MT). As predicted from the known properties of MT, this protein can compete with other sulfhydryl compounds for Cd but not for Hg; this is illustrated by the observation that glutathione (GSH) stimulates extrusion of only Hg. Similar factors can help explain why, in spite of its tighter binding by MT, Hg has a shorter biological half-life in renal cortex than does Cd. Metal extrusion from cells presumably involves movement of diffusible complexes such as HgGSH.