Role of protein adsorption in micropore passability of red blood cells.

Micropore passability of fresh human blood was measured by means of an improved Nuclepore membrane filter method under varying concentrations of electrolytes and proteins in the plasma. The method gives an average pore passage time required for single red blood cells to flow through 5 micrometers pores of the filter membrane. Micropore passability is reduced with increasing ionic osmolarity above 320 mOsM when the protein concentration is normal However, it remains constant up to 370 and 430 mOsM when the protein concentration is lowered to 1/3 and 1/6 of normal, respectively. Furthermore, when red blood cells are added to an hyperosmotic plasma, the protein concentration detectable in the plasma is reduced to a level lower than expected from a simple osmotic water shift. The excess reduction in the protein concentration is nearly proportional to the amount of added red blood cells. The following succession of events was assumed in order to interpret these results. An electric repulsive force between red blood cells and plasma proteins is weakened by an increased ion concentration. This reduction in this repulsive force will increase the adsorption of proteins on the surfaces of the red blood cells. The adsorbed proteins will restrict cell membrane flexibility, causing a reduced micropore passability of red blood cells.