Regulation of Erythropoiesis : XXIII. Dissociation between Stem Cell and Erythroid Response to Hypoxia

The effect of hypoxia on red cell production and stem cells, as measured by CFU, was studied in two strains of mice. One of these strains, the CAF₁, has been shown to produce relatively little erythropoietin in response to hypoxia; the other, the CF₁, produces substantial amounts of erythropoietin. In the studies reported herein the CAF₁ mice had an increase of ∼ 30 per cent in red cell mass after 23 days of exposure to either discontinuous (16 hrs./day) or continuous hypoxia equivalent to 23,000 feet of altitude. The CF₁ mouse doubled its red cell mass after similar exposure. The splenic CFU decreased to as low as 17 per cent in the poorly responding CAF₁ but remained at or near control levels in the CF₁. It is suggested that the dissociation between erythroid response and changes in the CFU reflect a secondary effect of hypoxia not directly related to the erythropoietin-induced increase in red cell production.