Lead transport and binding by human erythrocytes in vitro

Transport and binding of Pb²⁺ by human erythrocytes were examined for cell Pb contents in the 1–10 M range, using the ²⁰³Pb isotope. Pb²⁺ crosses the erythrocyte membrane by the anion exchanger, and can also leave erythrocytes by a vanadate-sensitive pathway, identified with the Ca²⁺ pump. However, Pb²⁺ exit is very much less than expected from earlier experiments with resealed erythrocyte ghosts [Simons TJB (1988) J Physiol (Lond) 405:105–113] and the distribution of Pb²⁺ across the erythrocyte membrane is close to equilibrium. The high ratio of erythrocyte to plasma Pb seen in vivo appears to be due to the presence of a labile Pb²⁺-binding component present in erythrocyte cytoplasm.