Stimulation of porphyrin accumulation in chick embryo liver cell cultures by partially purified erythroprotein

Step III and Step IV erythropoieten derived from sheep plasma stimulated the accumulation of porphyrins in cultured chick embryo liver cells. Increased porphyrin accumulation occurred within hepatocytes. It was not accompanied by increased hemoglobin formation. Stimulation of porphyrin accumulation was inhibited by hematin but was unimpaired by heating erythropoietin to 60°C for 10 min or preincubating it with trypsin. A more highly purified preparation of erythropoietin from human urine had no effect on porphyrin accumulation. The data indicate that a component in partially purified sheep erythropoietin can increase levels of a heme precursor in non-erythroid tissue. The participation of such a component should be considered when interpreting biochemical effects observed with crude erythropoietin preparations, other than ⁵⁹Fe incorporation into red cells or heme.