Granulocyte-macrophage colony-stimulating activity in the serum of estriol-treated mice

Granulocyte-macrophage colony-stimulating activity (GM-CSA) in mouse serum was examined after a single intraperitoneal injection with 10 mg estriol (E3). GM-CSA was detectable as early as 6 h after E3 administration and reached a peak by 24 h. Elevation of GM-CSA in the serum was maintained for at least 30 days. Using 0.1-10 mg of E3 there was a dose-dependent increase in serum GM-CSA when tested 24 h after E3 treatment. The majority of GM-CSA was adsorbed onto Concanavalin A-Sepharose 4B and was eluted by 0.2 M methyl-alpha-D-mannopyranoside, suggesting its glycoprotein nature. When E3-treated mouse serum was applied onto Sephacryl S-300 without any pretreatment, GM-CSA was detected as a sharp single peak with an apparent molecular weight of 440,000 daltons. When GM-CSA was treated with neuraminidase, however, and then applied to Sepharose CL-6B under disaggregating conditions (6 M guanidine HCl), the minimum molecular weight of the active component was estimated as 13,000 daltons.