Partial characterization of an erythropoiesis inhibitory factor.

An inhibitory factor of erythropoiesis, obtained from normal human urine, is indicated to be a complex of a fragment of alpha 1-acid glycoprotein and prostaglandin F2 alpha. Immunoelectrophoresis reveals two protein components in the EIF complex which separate during acrylamide gel electrophoresis. A gamma-globulin (MW 185,000) is a carrier of the complex. A fragment of alpha 1-acid glycoprotein (MW 9300) retains the inhibitory factor, PGF2 alpha. Noncovalent forces bind the PGF2 alpha to the protein, and PGF2 alpha can be extracted with benzene.