Red cell biochemical anatomy and membrane properties.

Abstract

Our understanding of the biochemical composition and organization of the red cell membrane has increased dramatically over the past two decades. Now that the membrane has been comparatively well characterized, it is possible to study the roles of specific membrane components in regulating the important biological membrane properties of deformability and stability. To fulfill its primary physiological function of oxygen delivery, the erythrocyte must be able to undergo repeated passive deformation. Its normally 8-JLm diameter must be altered to allow the cell to traverse capillaries with diameters of 2-3 JLm. In addition, the cell must have the capacity to resist fragmentation. These two essential qualities require a membrane that is extremely deformable yet very stable. Membrane stability can be defined as the maximum extent of deformation that a membrane can undergo and still completely recover its original shape. Beyond that degree of deformation, the membrane is unable to recover its predeformed state and it fails. An erythrocyte with normal mem­ brane stability can circulate without fragmenting, while a cell with decreased stability may fragment under normal circulatory stresses. Membrane de­ formability, on the other hand, determines the extent of membrane deforma­ tion that can be induced by a defined level of applied force. A more deform­ able membrane requires less applied force to enable it to pass through tiny capillaries. In this review, we focus on the recent developments in our understanding of which membrane components influence membrane deformability and stabil-