Effects of 5-fluorouracil on hematopoietic stem cells in normal and irradiated mice

The effects of 5-fluorouracil (5-FU) on hematopoietic stem cells (CFU-S) and nucleated cells in mouse femur and spleen were studied in normal and X-irradiated mice (ddY-SLC male, 8-10 weeks old). Changes in the number of circulating blood cells also were investigated in mice treated with 5-FU. A single dose of 5-FU (150 mg/kg) was injected i.p. The femoral CFU-S decreased after 5-FU treatment up to day 3 when it reached 2% of the control value. The cells then increased, reaching a maximum about twice that of control by day 12. A very similar profile was found for splenic CFU-S. Post-irradiation recovery for femoral and splenic CFU-S in mice treated with 5-FU 3 days before X-irradiation (1.9 Gy) was faster than in mice given irradiation alone. Regrowth rates of CFU-S were almost the same as in mice treated with 5-FU alone. The radiosensitivity of the CFU-S population in mice treated first with 5-FU at different times before X-irradiation (1.9 Gy) changed day-by-day after treatment. The maximal survival for femoral CFU-S was found in mice treated with 5-FU 5 days before irradiation, and for splenic CFU-S in mice treated 12 days before irradiation.