Evidence that asymmetry of the membrane/cytoskeletal complex in human red blood cell ghosts is responsible for their biconcave shape.

The main conclusion of the results reported in this article is that during centrifugation, sphered red blood cell ghosts become oriented in their attachment to a coverslip such that a dense band within the ghosts lies parallel to the centrifugal field. The result of the orientation of this dense band is that when the attached spherical ghosts are shrunken to become biconcave discs, they do so by directly collapsing on themselves without any lateral motion. This result is interpreted to suggest that a dense band, relative to the dimple, resides in the rim of the ghost and is responsible for its biconcave shape. These results confirm the conclusions reached in a previous publication in which there was the uncertainty that the shape change of the spherical ghosts to discs could not be directly imaged. The present work corrects this limitation by use of a chamber in which the tonicity of the solutions in the ghosts' surround could be altered by perfusion coupled with constant microscopic imaging. The identity of the components that are responsible for the differences in the density (mass) between the rim and the dimple regions of the cytoskeletal/membrane complex in the biconcave disk are unknown. It is also unknown what forces apply or what the explanation is for the unique orientation of the dense band during the ghosts' centrifugation, as described in this article. Nevertheless, the results reported in this article indicate the membrane's underlying cytoskeletal complex is asymmetrically distributed.