Uptake of 51Cr-chromate by human erythrocytes

Hexavalent chromium (Cr-VI), as Na2CrO4 in an aquous solution, was reduced rapidly to the trivalent form (Cr-III) in the presence of glutathione, GSH (0.3-3.0 mM). Such GSH-dependent reduction of Cr-VI can take place in the cytosolic space of Cr-VI-exposed cells, since GSH is found in reactive concentrations in this compartment. The reduction makes chromium essentially impermeable through the cell membrane, explaining the observation that Cr-VI, when added to red cell suspensions, is bound quantitatively intracellularly after a few hours. Diethylmaleate conjugation of the SH-group of the intracellular GSH preventing the oxidation to GSSG, lowered the chromium-uptake significantly, showing that reduced GSH plays a role for the chromium binding. In healthy red cells chromium is partially bound to haemoglobin and partially to small molecular weight substances, probably in the trivalent form. This intracellular chromium cannot be removed to the extracellular space by addition of chelating agents as long as the cell membrane is intact. (author)