Distribution of Cadmium in Human Blood Cultured in Low Levels of CdCI2: Accumulation of Cd in Lymphocytes and Preferential Binding to Metallothionein

Abstract

Human blood was exposed to low levels of CdCl2 (2 × 10-7M) in tissue culture. During a 3-day exposure, Cd was accumulated by the blood cells. Erythrocytes incorporated Cd to a level ~5-fold greater than the concentration in the growth medium, while lymphocytes accumulated Cd to a cellular concentration ~3000-fold greater than that in the culture medium. In erythrocytes, Cd was bound to several macromolecular species, none of which corresponded to the specific, inducible, Cd-binding protein me-tallothionein. In contrast, most of the Cd in lymphocytes was found associated with a low-molecular-weight macromolecule characteristic of Cd-thionein. On the basis of these studies showing the accumulation of Cd by lymphocytes and the metabolic response of lymphocytes indicated by the sequestering of Cd in metallothionein, it is possible that Cd exposure may alter normal immunocompetence associated with lymphocytes.