Hematopoiesis in the mEpoR^−/−, hEpoR⁺ mouse.

(A) Hematologic parameters for the mEpoR^−/−, hEpoR⁺ (hEpoR⁺) genotype were comparable to those of wild-type (WT) controls. (B) CFU-E colonies (left) and BFU-E, CFU-GM, and CFU-GEMM colonies (right) were determined for bone marrow hematopoietic progenitor cells (n = 5). (C) EpoR expression was determined for spleen (Spl), bone marrow (BM), brain (Br), and heart (Ht) for wild-type controls (mEpoR) (n = 3) and mEpoR^−/−, hEpoR⁺ (hEpoR) mice (n = 3), amol indicates attomoles. (D) Phenylhydrazine-induced (PHZ) anemia in mEpoR^−/−, hEpoR⁺ mice (n = 3) increased hEpoR expression in hematopoietic tissues and brain (n = 3 for control). (E) Results of stimulation of erythropoiesis in phenylhydrazine-treated mice were similar in mEpoR^−/−, hEpoR⁺ mice and controls as indicated by reticulocyte counts and hematocrit. Only differences in circulating erythropoietin levels (about 2-fold higher in mEpoR^−/−, hEpoR⁺ mice compared with controls) were detected. Serum erythropoietin levels in untreated mice were not detected in this assay because of the relatively low affinity of the antibody for murine erythropoietin.