Cadmium resistance and content of cadmium-binding protein in cultured human cells.

Abstract

INDUCTION of hepatic metallothionein (a cadmium-binding protein) is considered to be a protective mechanism in mammals against the toxic cadmium ion. Pretreatment of rats with low doses of cadmium induces the synthesis of metallothionein and also protects against subsequent exposure to an otherwise lethal dose1. But the role of metallothionein in cadmium resistance is not clear2. Restriction of food intake in the rat increases the level of metallothionein3, but does not alter the LD50 of cadmium2. Also the synthesis of metallothionein seems to continue for a longer time than the protection against cadmium in both rats and mice1,2. Lucis, Shaikh and Embil4 found uptake of Cd in cultured human embryonic fibroblasts, HeLa cells and monkey kidney epithelial cells after 8 d of incubation with Cd. At that time the cells also contained a Cd-binding protein. The authors did not, however, describe growth of the cells in the presence of Cd or development of cell strains resistant to Cd. Webb and Daniel5 recently described the synthesis of a Cd-binding protein in cultures of cells derived from the cortex of the adult pig kidney.