The effect of donor and cell age on several characteristics of rat erythrocytes.

Erythrocytes from young and old WF rats were separated by discontinuous density gradient centrifugation. The density and mean life span of the erythrocytes were correlated with cell age by 59Fe pulse labeling. A mean half-life of 40 and 25 days was measured for erythrocytes in young and old animals, respectively, with a corresponding 4-fold increase of young cells and a 2.3-fold increase in circulating reticulocytes in old animals. Thus, the old rat has a chronologically younger population of circulating erythrocytes than the young animal. The mean hemoglobin concentration of red cells from old, but not young animals, was found to decrease from 18.5 +/- 2.1 pg to 11.8 +/- 1.8 pg per cell with increasing cell age. Premature exposure of a surface antigen, which is recognized by antibodies present in the serum, was observed in cells of old animals. This antigen-antibody complex is presumed to trigger sequestration by phagocytosis of senescent erythrocytes. The contribution of the observed age-related changes to early erythrocyte sequestration in old animals is discussed.