Number of EpoR at the bone marrow cell surface and erythroid colony formation assay in differential concentrations of Epo.

(A) Number of radiolabeled recombinant human Epo binding sites at the surface of a bone marrow cell. Total mononuclear cells from the bone marrow of 4 to 8 mice at 10 to 12 weeks old were analyzed for each line. (B, C) Bone marrow cells were cultured for 3 days with different concentrations of Epo (B) or for 7 days with 50 ng/mL SCF and different concentrations of Epo (C) in methylcellulose medium. Erythroid colonies were counted by benzidine staining. *P < .01 compared with wild-type mouse.