Effects of recombinant human erythropoietin on DNA synthesis in rat hematopoietic organs.

In an attempt to define the effects of recombinant human erythropoietin (rEPO) on DNA synthesis in hematopoietic organs, we investigated DNA-synthesizing enzyme activities, i.e., thymidylate synthetase and thymidine kinase activities, and bromodeoxyuridine-immunohistochemistry during the recovery phase of hematopoietic cells in bone marrow and spleen after the hypoplastic period induced by cyclophosphamide (Cy) treatment in rats. Treatment with rEPO increased enzyme activities and cell number of erythroid series in bone marrow cells; it also increased organ weight and S-phase cells in the spleen, followed by an augmentation of the number of erythrocytes and a rise in the hemoglobin and hematocrit levels in peripheral blood with or without Cy treatment.