[Rubidium permeability through Ca2(+)-activated potassium channels in human erythrocytes]

Both potassium and rubidium can flow through the Ca2(+)-activated K channel of human erythrocytes. Although rubidium unitary currents are much smaller than potassium ones at the same potentials, no change in the reversal potential was observed on changing from potassium to rubidium solution on one side of the red cell membrane white keeping the other side in high potassium. The current-voltage curve in symmetrical potassium solutions exhibited strong inward rectification. When Rb+ was substituted for K+, the I-V curve became almost linear. These findings can all be described using a model with two binding sites, in which the ions are assumed to be both permeating and blocking.