SENSITIVITY OF THE BONE-MARROW AND SPLEEN HEMATOPOIETIC STROMA TO 5-FLUOROURACIL

We studied the effect of a single injection of 5-fluorouracil (5-FU) ( 150 mg/kg) on the numbers of stromal precursor cells (CFU-E) in the bo ne marrow and spleen and their capacity for formation of hemopoietic f oci after ectopic transplantation under the renal capsule. 5-FU decrea sed the number of CFU-F in the bone marrow and spleen of mice and rats to 30-50% of the control values. The size of transplants, as estimate d according to the number of hemopoietic clonogenic (CFU-S) and nuclea ted cells, diminished within the first two months after transplantatio n. Within four months after transplantation the size of the bone marro w transplants approached the control level, while that of the spleen t ransplants markedly exceeded the control level. Differences in the gro wth rate of regenerating transplants of the hemopoietic organs are dis cussed with special reference to the organ specific features of popula tions of the stromal cells.