Depressive effect of 7,12-dimethylbenz ) 7a{anthracene and ionizing irradiation on bone marrow colony-forming cells. )]

Treatment of neonatal inbred CFW/D mice with 7, 12- dimethylbenzSTAa!anthracene (DMBA) or gamma -irradiation suppressed the number of colony-forming units (CFUs) or stem cells in the bone marrow. At 14 days after administration, DMBA (30 mu g) had induced an 85% depression; at 60 days post treatment, there was still a 60 to 70% suppression. The extent and duration of the depression after the neonatal exposure to 400 rads (whole body) were similar. The permanent reduction in CFUs after neonatal irradiation contrasted sharply with the short-term effect of such a dose administered to adult animals. For both DMBA and irradiation treatment, the extent of the depression was dose dependent at low doses only. The effect of DMBA on the number of bone marrow stem cells was not merely quantitative: The CFUs remaining after treatment had a diminished ability to form spleen colonies on secondary transplantation. (auth)