Effect of Radiation on the Mouse Stem Cell Compartment in Vivo

Abstract

Different groups of hypertransfused mice were given different doses of whole-body irradiation. All animals received a standard challenge dose of 6 units of erythropoietin within 30 min after irradiation, and this initiated a wave of erythropoiesis, presumably by inducing differentiation of stem cells. The erythropoietic response was determined by measuring the incorporation into newly formed red cells of a tracer dose of radioiron given intravenously 48 hr after irradiation. The impaired erythropoietic response, as measured by the per cent of radioiron tracer, which uitimately appeared in newly formed red cells in the peripheral blood, decreased exponentially with increase in radiation dosage after an initial small shoulder at low doses of irradiation. Possible explanations are given for the early dip. The results tend to substantiate the conclusion that the primary action of ernhropoietin is upon the stem cell, inducing differentiation into the red cell series. (P.C.H.)