Regulation of erythropoiesis in the Friend leukemia mouse.

E VEN THOUGH THE IMPORTANCE of erythropoietin in the regulation of erythropoiesis has been established by a considerable quantity of information during the past decade,’8 whether or not erythropoietin is the sole regulating mechanism for erythropoiesis has been a subject of controversy. Although it is tempting to believe that erythropoietin production controlled by a feedback system (conducted by the oxygen supply to the tissue) determines red cell formation,9 the hypothesis cannot explain the compensated hemolytic syndrome,’#{176} the continuation of the erythropoiesis in the hypertransfused dog,’1 and the erythropoietic effect of hemi&2 or hemoglobin. Moreover, experimental studies showed that the erythropoiesis in the fetus14 or in the newborn’5 is governed by factors other than those seen in the adult. The Friend leukemia virus, isolated by Friend in 1956,16 has been shown to cause an increased erythropoiesis in the inoculated Swiss mice during their course of development of leukemia.’7 It was felt, therefore, that the study of the factors governing the increased erythropoiesis in the Friend leukemia would contribute to the understanding of erythropoiesis in pathological states. Iii the present work, the hematological changes occurring in the ddO mice after the inoculation of the Friend virus have been followed. Having confirmed the occurrence of erythrocytosis in the infected ddO mice, the nature of this increased erythropoiesis was studied by rendering them polycythemic through transfusion.