Some aspects of iron metabolism during erythropoietic depression in the mouse.

Spleen and bone marrow patterns of response differ in mice subjected to erythropoietic depressors. Radioiron injected a few hours after a high dose of cyclophosphamide or x-irradiation is retained in the bone marrow. The magnitude of medullary retention is closely related to the number of cells able to synthesize hemoglobin at the moment of iron administration, and to the rate of cell death provoked by the cytotoxic agent. Depressors such as Actinomycin and transfusion, that block the differentiation of stem cells while allowing normal maturation of the erythroid cohort, do not induce marrow entrapment of iron. By contrast, retention is never observed in the spleen, where the 59-Fe turnover is not influenced by the mechanism and magnitude of aplasia. A functional lack of homogeneity of splenic and bone marrow erythropoiesis, hemoglobin metabolism and/or handling of iron stores is proposed. These results would be in agreement with other data from the literature reporting physiological differences among the various sectors of the reticuloendothelial system.