Early reactions of cadmium with Ehrlich cells

Ehrlich ascites tumor cells accumulate cadmium against a concentration gradient in a bisphasic uptake process. There is little efflux of the metal from preloaded cells into a cadmium-free medium. Incorporation of 3H-thymidine into DNA is markedly inhibited by cadmium ion at 5-100 ng atoms of Cd/mg of cell protein, but uptake of the nucleoside label into cells is not depressed in this concentration range. Cell respiration is much less affected by cadmium ion despite the sensitivity of isolated mitochondria to the metal. Model experiments using several cadmium complexes with known conditional formation constants show that bovine heart mitochondria have strong affinity for cadmium ion. The contrast between this result and the resistance of cells to respiratory inhibition with cadmium ion is discussed to illustrate the difficulty in relating in vitro studies to the cell. The behavior of cadmium ion with the Ehrlich cell is compared with data for zinc ion to reveal similarities in inhibition of nucleoside metabolism and respiration but a sharp difference in transport properties.