Homogeneous interleukin 3 enhances arginase activity in murine hematopoietic cells

Incubation of murine spleen and bone marrow cells with homogeneously purified interleukin 3 (IL-3) results in increased urea and ornithine production. This phenomenon is explained by a marked enhancement of arginase activity, assessed by transformation of labeled arginine into labeled urea during culture and by intracellular arginase assay. The enhancement of enzymatic activity is evident after 12 hours of incubation with IL-3, reaching a maximum after 24 hours. It is (1) dose dependent, (2) restricted to cells from hematopoietic organs (i.e., spleen and bone marrow), and (3) independent of cell proliferation, since irradiation of bone marrow cells does not abolish the arginase enhancing effect of IL-3 in spite of complete inhibition of proliferation. Furthermore, this new activity is specific to IL-3, since other colony-stimulating factors, i.e., granulocyte-macrophage colony-stimulating factor (GM-CSF) and L cell-derived colony-stimulating factor (L-CSF), do not induce it.