THE USE OF 59Fe UPTAKE FOR THE EVALUATION OF CELL PROLIFERATION IN SPLEEN COLONIES

A technique of 59Fe uptake in the spleen of irradiated bone‐marrow‐transplanted mice has been applied to the study of some kinetic parameters of the erythroid spleen nodule cells. Measurements of the doubling time of this population have been obtained together with estimates of radioactivity disappearance from the spleen, owing to a release of nodule cells into the blood stream. The kinetics of expansion of the erythroid cell compartment is compared with the pattern of increase of the colony‐forming cells in the spleen. The expansion of the erythroid cell population seems to be the result of at least two processes: an increase in the number of differentiating cells and the release of mature cells into the blood stream. It is suggested that more refined attempts to evaluate kinetic parameters of the spleen nodule cell population should allow for these factors.