Inhibition of erythropoiesis by plasma component(s) from sheep, goats, and rabbits.

Plasma from hypertransfused and normal sheep and experimentally induced anemic and normal goats was fractionated by ultrafiltration. Fractions obtained were assayed for erythropoiesis stimulatory factor (ESF) or erythropoiesis inhibitory factor (EIF) activity (or both) in the posthypoxic polycythemic mouse assay. The most potent sheep plasma-inhibitor fraction was found in the retentate on a membrane with a cutoff at mol wt 50,000. The most potent EIF fraction from anemic goats passed into the ultrafiltrate, but the comparable EIF from normal goats remained in the retentate on a membrane with a cutoff at mol wt 500. The yield of the most potent EIF fraction was higher from anemic goats than was the yield from normal goats. During thin-layer chromatography, EIF extracted from goat plasma fractions had the same mobility as did prostaglandin F2 alpha. Cohn rabbit plasma fraction IV-4 had an inhibitory factor, and a benzene extract of the fraction contained a component that had the same mobility as did prostaglandin F2 alpha. Cohn rabbit plasma fraction V contained a component that potentiated an erythropoietin-generating factor.