Comparison of cell proliferation in the regenerating bone marrow and spleen of irradiated mice with the use of 125I-iododeoxyuridine.

The method of 125IUdR labelling of hemopoietic cell populations was used to estimate differences of repopulation kinetics in the femoral bone marrow and spleen of sublethally irradiated mice. In regenerating bone marrow the cellularity and proliferation index, as measured by 6 h 125IUdR incorporation, were found to be inversely related. In the spleen the proliferation index increased parallelly with the increase in cellularity and indicates an ineffectiveness of a change in the set point of local cellularity control. Experiments with measuring the retention of 125IUdR in hemopoietic organs revealed, in the spleen of irradiated animals, phases of increased cell losses as well as immigration of labelled cells into this organ.