Changes in potassium permeability and membrane potential of bovine red blood cells estimated by the use of a dimerizing fluorescence probe.

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Abstract
The partition of 3,3''-dipropyl-2,2''-thiadicarbocyanine, diS-C3(5), between the interior of bovine red cells and bulk aqueous medium was measured by using fluorescence spectroscopy. Inside the cells (concentrated Hb phase), diS-C3(5) is intensely concentrated and consequently forms the nonfluorescent dimer. Valinomycin stimulates K+ transport across the cell membrane and the resulting change in membrane potential induces an alteration of the partitioning and the dimerization of diS-C2(5). The changes in membrane potential and permeability of the red cell membrane to K+ were quantitatively associated with this dimerization. The permeability of the membrane to K+ estimated here can be correlated with the characteristic properties of the bovine red cell membrane, i.e., the high content of sphingomyelin and the rigidity of this membrane.