Factors influencing hematopoietic spleen colony formation in irradiated mice. IV. The effect of erythropoietic stimuli

Abstract

A variety of erythropoietic stimuli influenced the number of endogenous spleen colonies in irradiated mice and the number of transplantable colony forming cells in the spleen and marrow of unirradiated mice.Bleeding was the most effective stimulus. Bleeding before irradiation resulted in a 30‐fold increase in endogenous spleen colonies and in increases in spleen weight, spleen iron and iododeoxyuridine uptake and volume of packed red cells ten days after irradiation. Bleeding unirradiated mice produced a 10‐fold increase in the number of transplantable colony forming cells in the spleen and a slight decrease in the total number in the humerus. Bleeding before irradiation resulted in a significant reduction in 30‐day post irradiation deaths, an effect abolished by splenectomy. Plasma from bled mice induced an increase in endogenous colonies when injected before irradiation into normal mice.Injection of erythropoietin, testosterone or testosterone plus cobalt induced effects which were, in general, qualitatively similar to those of bleeding, although they were less effective quantitatively. Except for a slight effect induced by ten injections of erythropoietin, post‐irradiation stimulation in normal mice proved ineffective. Erythropoietin increased colony numbers and spleen iron uptake when given after irradiation to hypertransfused mice.The results of these studies do not support the concept that the colony forming cell and the erythropoietin sensitive cell are separate entities.