Extraction of an Erythropoietin-Producing Factor from a Particulate Fraction of Rat Kidney

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Abstract
A two-step method for the extraction of erythropoietin from hypoxic kidneys was developed which allows separation of residual plasma erythropoietin in renal vasculature from intracellular origin. Renal extracts were purified by DEAE [diethyl ammoethyl] cellulose chromatography and contained 2 major erythropoietically active fractions. This activation phenomenon identifies this kidney component as the renal erythropoietic factor (REF). REF produces erythropoietin or becomes erythropoietically ac?ive when incubated with normal rat serum. Differential eentrifugation technics revealed that the REF is confined to particles present in the light mitochondrial fraction of kidney. Extracts of the light mitochondrial fraction of kidneys from normal rats produced significant amounts of erythropoietin when incubated with normal serum. The quantity, was less than similar extracts of kidneys from hypoxic rats. The product of the incubation extracts of the renal light mitochondrial fraction with normal rat serum showed the same log dose/ response regression as sheep plasma erythropoietin standard. Either the REF is a precursor of erythropoietin, complexed with a carrier present in normal serum and becoming physiologically active, or the renal factor is an enzyme which produces erythropoietin by its action on a particular serum protein.