Regulation of erythropoiesis. XXI. The effect of erythropoietin on the stem cell.

SummaryNine units of erythropoietin given in equally divided doses at 8-hour intervals for 23 days to the CAF1 mouse produced a significantly greater polycythemia than had been observed in this strain when exposed to 23,000 feet for a similar period of time. The splenic CFU began to increase within 24 hours after the beginning of treatment and reached levels of 5-fold those of controls between days 8 and 16. The extent to which migration of CFU from the marrow and or replication of CFU in situ is responsible for the increase in splenic CFU is discussed. It is concluded that the stem cell participates in the physiologic response to erythropoietin but without depletion of this compartment. The possibility that the previously reported decrease in CFU in hypoxic animals represents a secondary perhaps “toxic” effect of hypoxia unrelated to erythropoietin is considered.