On the estimation of the thickness of the red cell membrane from ultracentrifuge studies

Abstract The assumptions underlying the ultracentrifuge method for determining the thickness of the red blood cell membrane are criticized. It is suggested that the collapse of the ghost by the action of the centrifugal force is prevented by the countereffect of the osmotic pressure inside the ghost, hence the volume of the packed ghosts is no indication as to the volume of the cell membrane or stroma. Experiments with saponin treated ghosts and with untreated ghosts showed that the volume of packed untreated ghosts remained constant throughout the whole range of centrifugal force applied, up to about 270,000 g . Saponin treated ghosts, on the other hand, collapsed under the influence of the centrifugal force and were packed into a small fraction of the volume of the untreated ghosts. It is concluded that ghosts prepared by osmotic hemolysis of red blood cells in hypotonic salt solutions have a thin semipermeable membrane with respect to salts in aqueous solution.