KINETICS OF ERYTHROID AND MYELOID STEM CELLS IN POST HYPOXIA POLYCYTHEMIA

The number of erythroid burst- (BFU-E) and colony-forming units (CFU-E), as well as of myeloid-macrophage colony-forming units (CFU-C), was evaluated in tibial marrow and spleen of ex-hypoxic polycythemic mice, at sequential time intervals after the end of hypoxia. In both marrow and spleen, the kinetics of the CFU-E pool is characterized by a sharp fall from above normal to lower than normal values. BFU-E and CFU-C rose from below normal to higher than normal levels. These results were correlated with both the erythropoietin (Ep) and the erythropoietic activity curves. Ep levels apparently largely control both the differentiation and the amplification of the CFU-E pool and its is suggested that Ep may act as a survival factor at the CFU-E level and/or increase the flow of cells from BFU-E to CFU-E. The difference in response between CFU-E and BFU-E favors a clearcut distinction between these populations, but the similarity between the BFU-E and CFU-C response suggests a close relationship between these 2 cell populations. The murine spleen functions as a large reservoir of erythroid microenvironment for hypoxia-induced stress erythropoiesis.