Chromatographic techniques for the separation of a thrombocytopoiesis-stimulating factor from aplastic rats

Thrombocytopoietin seems to be only partially responsible for the regulation of platelet production. We determined precisely the differences between a second thrombocytopoiesis-stimulating factor (TSF2), and thrombocytopoietin (TSF1) and erythropoietin (Epo). Fractionation was carried out, first on a DEAE-cellulose phosphate column and then on a Sephadex G-75 column. Thrombocytopoietic activity in the various fractions was assessed using 75Se-methionine platelet incorporation into normal recipients. Epo concentrations were determined using a radioimmunoassay. We showed that the apparent molecular weight of TSF2 is 14,000 daltons. It differs from TSF1 (48,000 daltons) and from Epo (39,000 daltons). For doses of 8-12 mU Epo/rat, found in whole serum injected, no effect on thrombocytopoiesis was found. On the contrary, a significant effect (p less than 0.01) was found when the same quantities of Epo present in the Sephadex G-75 F4' fraction were injected (2-10 mU/rat). TSF2 can be separated from TSF1 and Epo, using biochemical techniques.