Dex enhances proliferation and colony-forming ability of erythroid progenitors. (A) Human bone marrow cells were cultured in medium complemented with Epo, SCF, IGF-1, and either Dex or ZK (□ and ▪, respectively). (B) At days 0, 4, and 8, cell aliquots of both cultures were seeded in fibrinogen clots with 2, 5, and 15 cells per well and medium complemented with Epo, SCF, IGF-1, and either Dex or ZK (indicated by D or Z at the X-axis) was added. Previous liquid culture conditions are indicated below by Dex or ZK. After 10 days, colonies were stained with benzidine and counted, and the cell number per colony was estimated as small (0 to 30 cells), medium (30 to 100 cells), or large (>100 cells). Colony number is given per 100 bone marrow cells seeded in the culture at day 0. The number above the bars indicates the percentage of only partially hemoglobinized colonies.