Influence of lead ions on cation permeability in human red cell ghosts

Summary

Intracellular Pb²⁺ ions can replace Ca²⁺ ions in stimulating the Ca-dependent K permeability of human red blood cells. In metabolically depleted resealed ghosts, the threshold for stimulation of⁸⁶Rb efflux by internal Pb²⁺ is around 5×10⁻¹⁰ m, and stimulation is half-maximal at about 2×10⁻⁹ m, and maximal at 10⁻⁸ m Pb²⁺. There is no effect on²²Na efflux in this concentration range.⁸⁶Rb efflux is antagonized by internal Mg²⁺ ions, and by the channel-blocking drugs quinidine and diS-C₂(5), as observed for the Ca-dependent K permeability in red cells. In ghosts containing EDTA, which prevents any internal effects of Pb²⁺ ions, external Pb²⁺ increases both²²Na and⁸⁶Rb permeability when its concentration exceeds 6×10⁻⁷ m. This effect is seemingly unrelated to the Ca-dependent K permeability. This work makes extensive use of Pb²⁺ ion buffers, and gives information about their preparation and properties.