In vitro studies of erythropoietic progenitors (CFU-E) in marrow from neonatal and young mice.

Reports that cells from neonatal animals produce CFU-E in response to erythropoietin (Ep) at doses lower than are required by adults indicated that young mice would provide a good system to study the hormone response of erythropoietic progenitors. Studies presented here confirm the increased Ep responsiveness until 3-4 weeks of age reported previously by others. Along with the enhancement in their Ep responsiveness, bone marrow cells from young animals produce many more CFU-E per 10(5) cells plated than do adult animals; i.e., neonates have a higher plating efficiency for CFU-E in the presence of erythropoietin. Neonatal animals, in contrast to adults, contain in addition erythropoietic progenitors in their bone marrow capable of growth in vitro without added hormone. Because of the large numbers of "endogenous" colonies, a study was done to explore the possibility that a small amount of Ep was present in the culture medium. Antiserum to erythropoietin was added directly to cultures in another study to remove any undetected hormone. The results indicate that CFU-E from neonatal mouse bone marrow can develop in culture in the absence of detectable Ep.