Persistent macrocytosis assessed by erythrocyte subpopulation analysis following erythrocyte regeneration in cats

Serial erythrocyte volume distribution curves were used to characterize changes in erythrocyte subpopulations following the induction of Heinz body hemolytic anemia in cats. Macrocytes produced in response to hemolysis were observed after loss of reticulum. After recovery from hemolysis, a gradual reduction in mean cell size resulted from a combination of macrocyte remodeling and production of normocytic cells. The mean apparent prehemolysis half-survival time for chromium-51- labeled erythrocytes was 13.7 days. There were two components to the posthemolysis survival curve. An initial accelerated loss of label was due to either destruction of posthemolysis macrocytes or loss of cell contents associated with remodeling. The second survival curve component reflected an increased mean apparent half-survival time of 20.2 days. After correction for isotope elution, the latter component reflected cohort-like labeling of relatively young erythrocytes having normal survival for the duration of the experiment. At the beginning for this latter component, 42% of the erythrocytes were macrocytic (mean of 3.3 x 10(6) macrocytes/microliter). Since the number of macrocytes gradually declined during the period of normal survival, it was concluded that these cells entered the normocytic size range. Recognition of persistent macrocytosis is important in the concept of the regenerative response and should be considered in the interpretation of erythrocyte volume distribution curves.