The effect of LiCl or zVAD-FMK on growth factor–deprived erythroblast clonogenicity.

Equal numbers of erythroblasts on day 5 to 6 of culture were washed and treated for 8 hours in medium with no growth factors, Epo 2 U/mL and SCF 20 ng/mL (ES), or no growth factors and LiCl (20 mM) or zVAD-FMK (100 μM) as indicated. Cells were then returned to normal medium supplemented with Epo 2 U/mL and SCF 20 ng/mL in 96-well plates at a predicted density of 0.66 cells/well. The mean percentage ± SEM of wells yielding a colony of 4 cells or more 72 hours later is indicated (n = 4).