Retention of radiolead by human erythrocytes in vitro

An in vitro method was developed to assess human erythrocyte lead uptake and release directly, rapidly, and reproducibly; the technique requires small aliquots of blood and uses silicone fluid to separate erythrocytes from their suspending media. Uptake occurred rapidly and was directly related to temperature. Increasing quantities of available elemental lead were associated with increasing absolute quantities but decreasing percentages of uptake. Low values of pH diminished the uptake and enhanced the release of radiolead by erythrocytes, and could be correlated with diminished lead-hemoglobin binding para-Chloromecuribenzoate increased and dithiothreitol inhibited radiolead uptake but neither compound affected lead release, suggesting that sulfhydryl groups are important for lead binding to the erythrocyte. Cyanamide and N-ethylmaleimide did not significantly affect the net uptake or release of radiolead. Calcium disodium EDTA, penicillamine, and dimercaprol significantly reduced lead uptake, although only incubation with dimercaprol resulted in a net removal of lead from erythrocytes. Iron and ceruloplasmin significantly decreased radiolead uptake, but inorganic metal cations other than iron, hyperosmolarity, human serum albumin, cholesterol, and transferrin had no significant effect on uptake or release.