A "serum-free" medium for the production of erythropoietic bursts by murine bone marrow cells.

We describe a culture medium that does not require the addition of serum, in which erythropoietic bursts are produced from murine bone marrow cells with efficiencies at least as great as those of serum-containing media. Four ingredients were shown to be essential: bovine serum albumin (BSA), transferrin, cholesterol, and erythropoietin. The system supported burst formation without the addition of conditioned medium as source of burst-promoting factor(s). To include cholesterol in the medium we found that there was no necessity for sonication, nor for subsequent evaporation of the ethanol in which the cholesterol was dissolved. Filtration of cholesterol and delipidation of BSA both impaired the ability of the medium to support burst production. The "serum-free" medium described here, even though not truly defined, is useful for erythropoietic culture: it is reliable, highly efficient in supporting burst formation, and simple and economical to prepare from ingredients readily available from commercial sources without the need for special testing.