Erythropoietic inhibitory activity of plasma fractions from hypertransfused sheep.

The plasma and serum of polycythemic animals and man are reported to exhibit erythropoietic inhibitory activity in certain bioassay systems. The plasmas of hypertransfused and normal sheep were fractionated by the methods of Cohn and Weimer and their associates, and the major fractions assayed for stimulatory or inhibitory activity in the exhypoxic polycythemic mouse assay system. The results indicate that the inhibitory activity acquired with hypertransfusion can be demonstrated in fraction VI of Cohn's and in precipitate of D of Weimer's methods and that the activity of each is retained in the eluates from G-200 Sephadex columns.