Effect of membrane dialysis and filtration-sterilization on erythropoietin activity.

Most erythropoietin (Ep) preparations contain non-erythropoietin contaminants. The use of such hormone concentrates raises important questions regarding interpretations of results derived from in vivo and especially from in vitro studies. By sterilizing various Ep preparations with Nalgene, Millipore, or Selas silver filtration, or even after conventional membrane dialysis, variable responses were noted when the Ep was assayed with mouse bone marrow cells in vitro (i.e. by stimulating the production of erythroid colonies from CFU-e and BFU-e) and in vivo (i.e., by using the exhypoxic, polycythemic mouse bioassay for Ep). The utility and limitations of such preparative procedures are discussed.