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

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Abstract
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 5×10−10m, and stimulation is half-maximal at about 2×10−9m, and maximal at 10−8m 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 6×10−7m. 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.