Cadmium uptake by rat red blood cells.

Rat red blood cells were employed to study the uptake of cadmium (109Cd). Suspensions of red blood cells were exposed to Cd concentrations of 0.005-500 microM, which were representative of whole blood concentrations (both bound and free) observed following in vivo Cd administration. Cd uptake was biphasic with an initial rapid phase (less than 1 min) followed by a slower second phase. The rate of Cd uptake at 25 degrees C was one-fourth of that at 37 degrees C. The metabolic inhibitors; sodium fluoride (1 mM), potassium cyanide (1 mM) and carbonyl cyanide-m-chlorophenyl hydrazone (2 microM) and the Na+-K+-ATPase inhibitor, ouabain (1 mM) did not reduce Cd (50 microM) uptake into red blood cells. This suggests that the uptake of Cd into red blood cells was not an active process. Incubation of Cd (10 microM) with an equimolar concentration of Zn did not alter uptake of Cd into red blood cells, but at 5 and 10 times higher concentrations of Zn, Cd uptake was enhanced 5-fold. Mercury at one-tenth and equimolar concentrations of Cd increased Cd uptake by red blood cells 2-fold. N-Ethylmaleimide (0.5-5 mM), which irreversibly inactivates membrane sulfhydryl groups, decreased Cd uptake. The data indicate that Cd uptake into rat red blood cells occurs by passive transport and that alterations of sulfhydryls of red blood cell membrane may modulate the process.