Sodium and Potassium in Human Red Cells Variations among Centrifuged Cells

Abstract

Separation of human red cells in fractions of different densities was obtained by centrifugation. Prior to the determination of red cell sodium, potassium, and water, trapped extracellular sodium was washed off, using an isotonic sodium-free solution. This method is described in some detail. High density cells had lost potassium and water. Potassium was lost in excess leading to a decrease in cellular potassium concentration. The cellular sodium content was not influenced by cell density, but as a consequence of the water loss, the sodium concentration was increased in the high density cells. While the density-related changes were dominated by the cellular loss of potassium and water, the changes related to digoxin treatment and to hypokalaemia were characterized by an equimolar increase, respectively decrease, in red cell sodium and potassium concentrations (density unchanged); the digoxin-and hypokalaemia-related changes were evenly distributed on the different density fractions and thus independent of cell density. Provided that the high density cells are stable cells in steady state, an increase in potassium permeability combined with an inhibition of active sodium and potassium transport might explain the observed changes in red cell sodium and potassium in the high density cells.