Erythrocyte aging: physical and chemical membrane changes.

The mammalian erythrocyte is an interesting model for studies of membrane aging. Experimental approaches to this problem involve, first of all, comparison of properties of erythrocytes separated by density because red blood cell age correlates with density in principle. Other approaches to study red cell membrane aging, such as hypertransfusion, are also discussed. A number of physical and chemical changes occur in erythrocytes with aging. Crucial to the elucidation of aging mechanisms is to determine which are primary and which are secondary. Immunoglobulin G binding triggers cellular removal and seems necessary for the recognition of senescent erythrocytes. Cellular deformability decreases while fragility to hemolytic factors generally increases and surface charge density does not alter. Perhaps more important are reactions of reactive oxygen species with membrane constituents and subsequent proteolysis. These are implicated as causative factors in red cell aging, immunoglobulin binding and recognition of senescent erythrocytes.