BIOLOGICAL PROPERTIES OF THE COLONY-PROMO TING ACTIVITY IN EXTRACTS PREPARED FROM MURINE KIDNEY

Aqueous extracts prepared from the murine kidney (MKE) promoted colony formation derived from murine hematopoietic progenitor cells in serum -free cultures stimulated by interleukin-3 (IL-3) and erythropoietin ( Epo). MKE itself did not stimulate any colony formation. MKE preferent ially enhanced granulocyte-macrophage colony forming units (CFU-GM), b ut did not promote any erythroid colony formation. The CFU-GM colony p romotion by MKE was observed at day 6 after the culture started, and t he colony-promoting activity (CPA) was maintained at the same level un til day 16. MKE showed no CPA in the cultures using cells obtained fro m 5-FU-injected mice and from c-kit(+)-enriched treatment. Furthermore , MKE acted synergistically with granulocyte-colony-stimulating factor (CSF), macrophage-CSF, IL-6 and IL-11 on colony formation, but did no t act with GM-CSF, stem cell factor and Epo. From the results of vario us experiments and gel-filtration chromatography, it is estimated that the colony-promoting factor detected in MKE is a heat stable protein with about 20 KDa molecular weight. These results suggest that MKE pro motes colony formation by murine myeloid progenitor cells, and that th e target cell. populations of MKE are relatively mature in the hematop oietic differentiation pathway.