Effects of 5-FU on changes in hemopoietic cell populations. (A) Flow cytometric analysis of bone marrow cells. 7-wk-old mice were injected with vehicle (top) or 5-FU (250 mg/kg body weight; bottom). 8 d after the injection, mice were killed. Bone marrow cells prepared from tibiae were analyzed for the expression of MOMA-2 and CD11b (left) and c-Fms and RANK (right). The numbers in the top right corners indicate percentages of MOMA-2⁺/CD11b⁺ cells or of c-Fms⁺/RANK⁺ cells among all bone marrow cells. Results are expressed as the mean ± SD for three animals. (B) Effects of HU on osteoclast formation. MOMA-2⁺/CD11b⁺ cells and c-Fms⁺/RANK⁺ cells were isolated from bone marrow of wild-type mice by magnetic cell sorting and cultured in the presence of 10⁴ U/ml M-CSF and 100 ng/ml RANKL. 70 µM HU was added to some cultures. After 6 d of culture, cells were fixed and stained for TRAP. TRAP⁺ multinucleated cells containing more than three nuclei were counted as osteoclasts. Results are expressed as the mean ± SD for six cultures. *, P < 0.01; significantly different from the culture incubated without HU.