Postirradiation Hemopoietic Repopulation and Stromal Cell Viability

To evaluate some of the microenvironmental conditions necessary to support hemopoiesis, the right femurs of mice were X-irradiated. Femoral radioiron uptake in the right femur after 1000 rad fell to 20 ± 2% of the control (mean ± 1 SEM) at 3 days and returned to 67 ± 5% by 6 months. Erythroblast counts reflected these changes. Total nucleated cell counts initially diminished to 21 ± 3% of the control but increased to 76 ± 6% of normal by 6 months. Counts of bone marrow stromal cells in culture rose from 13 ± 4% of the control at 3 days to 77 ± 11% by 6 months. In contrast, except for temporary elevation in 59 Fe uptake at 1 week, animals receiving 5000 or 10,000 rad to the right femur had persistently low levels (