Evaluation of some serum erythropoietin concentration procedures using serum-containing and serum-free in vitro bioassays

Studies are reported which were designed to further refine a serum-free culture method to assess the erythropoietic response of fetal mouse liver cells. The objective was to employ such a serum-free system with deproteinized serum concentrates as the test materials in a potentially highly specific assay for erythropoietin (Ep). A serum-free culture method is described which permits responses to Ep (125I-deoxyuridine incorporation) closely comparable to those observed in cultures containing optimal concentrations of sera. Mean recoveries of Ep were acceptable in each of three variations of a serum concentration procedure. However, no correlations were evident between Ep titers in whole sera and those in the concentrates (assayed in both serum-free and serum-containing cultures) with deproteinization and/or concentration procedures involving serum acidification and exposure to boiling water temperature.