Partial purification of a thrombocytopoietic-stimulating factor from kidney cell culture medium

Abstract Thrombopoietin (TSF)-rich kidney cell culture media were subjected to fractionation by ammonium sulfate precipitation and Sephadex column chromatography. The fractions thus obtained were tested for TSF content in thrombocytotic mice using Na 2 35 SO 4 as a platelet label. Proteins precipitated by 40–60 and 60–80% ammonium sulfate saturation caused significantly increased platelet counts and 35 S incorporation into platelets of assay mice. However, injections of saline, control media, or the proteins precipitated by 0–40 and >80% ammonium sulfate saturation did not stimulate thrombocytopoiesis in mice. In experiments using Sephadex G-100 columns, materials eluted from columns with V e V o (elution volume/void volume) values in the range of 1.5–2.4 were shown to contain the thrombocytopoietic factor. TSF from kidney cell culture media was not dialyzable and did not deteriorate in both ammonium sulfate and Sephadex fractions during 4–5 weeks of storage at −76°C. The results of this study indicate the feasibility of utilizing media from kidney cell cultures for the production of a stable, biologically active TSF that can be partially separated from other proteins.