Studies on the Adhesiveness of in vivo Aged Erythrocytes

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Adhesiveness of in vivo aged erythrocytes was studied by measuring (i) the velocity of erythrocyte aggregation and the dissociation of the aggregates, and (ii) the interaction of erythrocytes with artificially reproduced erythrocyte membrane on the glass plate.(1) Human aged erythrocytes fractionated by a density gradient centrifugation with Percoll were more aggregative and more adhesive than young erythrocytes.(2) Aggregation velocity of erythrocytes normally produced in rats was greater in plasma than that of erythrocytes produced in recombinant human erythropoietin-administered rats (in which young erythrocytes were produced in bone marrow by erythropoietin stimulation).(3) Importance of membrane surface structure of erythrocytes, particularly, the great contribution of the structural change of glycophorin A, was shown for the erythrocyte aggregation and the adhesiveness among erythrocytes. The phenomena were proposed as a model of in vivo aged erythrocytes, with a special regard to survival of erythrocytes in circulation.In conclusion, increased adhesiveness of erythrocytes during in vivo aging in addition to the decreased deformability contributes to the removal of these aged erythrocytes in the reticuloendotherial system. In the process of impaired passage of aged erythrocytes in the reticuloendothelial system, the structural change of surface membrane proteins of the erythrocytes (the appearance of "senescent antigen" ) is sensed by macrophages.