Erythropoiesis in vitro. III. The role of potassium ions in erythroid colony formation.

The role of potassium as an essential promotor of erythroid progenitor growth (BFU-e & CFU-e) from normal murine hematopoietic tissues was studied. Dialyzed fetal calf serum, over a wide range of concentrations, was shown to reduce the numbers of BFU-e and CFU-e that could be cultured from normal murine bone marrow. A dose-dependent addition of 1 M KC1 restored erythroid progenitor colony growth to the levels generally seen when normal, non-dialyzed fetal calf serum was used. Furthermore, when [K] was increased in some human urinary and sheep plasma erythropoietin preparations, the number of erythroid progenitor cells cultured also increased. This influence is crucial to the differentiation of committed stem cells into the erythroid pathway and must therefore be considered in the development of serum-free growth media.