Study of the effect of the administration of Cd(II), cysteine, methionine,and Cd(II) together with cysteine or methionine on the conversion of xanthine dehydrogenase into xanthine oxidase

Cadmium is known as to be a potent pulmonary carcinogen to human beings and to induce prostate tumor. The sequestration of cadmium, an extremely toxic element to living cells, which is performed by biological ligands such as amino acids, peptides, proteins or enzymes is important to minimize its par ticipation in such deleterious processes. The synthesis of metallothionein is induced by a wide range of metals, in which cadmium is a particularly po tent inducer. This protein is usually associated with cadmium exposure in m an. Because metallothioneins may act as a detoxification agent for cadmium and chelation involves sulfur donor atoms, we administered only cadmium, cy steine, or methionine to rats and also each of these S-amino acids together with cadmium and measured the production of superoxide radicals derived fr om the conversion of xanthine dehydrogenase to xanthine oxidase. It could b e seen in this work that the presence of cadmium enhances this conversion. However,its inoculation with cysteine or methionine almost completely dimin ishes this effect and this can be the result of the fact that these amino a cids complex Cd(II). Thus, these compounds can be a model of the action of metallothionein, removing cadmium from circulation and preventing its delet erious effect.