The effect of an osmotic pressure gradient and lysophosphatidylcholine on the transient and constant potassium permeability properties of the erythrocyte membrane.

The rate constant of 86Rb efflux and total potassium release from erythrocytes under the influence of lysophosphatidylcholine (LPC) and osmotic pressure gradients were compared. Both osmotic pressure gradients and LPC caused a transient increase in the potassium permeability of the erythrocyte membrane. In hypotonic media without or in the presence of LPC this sudden increase is completely reversible, since the rate constant of rubidium efflux from unhaemolyzed cells, which is an indicator for the continuous potassium release, remained the same as measured in an isotonic NaCl medium without detergents. The potassium release was more pronounced in the presence of LPC and may have a protective effect against haemolysis. In an isotonic NaCl or sucrose medium, LPC caused a transient potassium release probably due to incorporation of LPC into the membrane and vesicle release, but also an increase in the rate constant of rubidium efflux due to change in the membrane structure connected with vesicle release.