Separation of erythropoietin responsive cells in fetal mouse liver

The erythropoietin responsive cells (ERC) in suspension cultures (ERCSC) of fetal mouse liver and the cells producing erythroid colonies in 2-day plasma clot cultures (CFU-E) sediment at similar rates. However, the sedimented fractions containing the majority of nucleated cells show minimal sensivitity to erythropoietin (Ep) and these cells sediment at a slower rate than the ERCSC. The studies suggest that in short-term suspension cultures of fetal mouse liver, Ep acts on morphologically unrecognizable cells to increase the number of hemoglobin-synthesizing cells rather than by increasing the quantity of hemoglobin synthesized per cell. This effect is similar to the principal in vivo action of Ep.