Abstract
Summary
Plasma from anemic rabbits containing erythropoietic stimulating factor was treated in numerous ways in order to determine some of the properties of the factor. Assay was performed by determining the Fe59 uptake in hypophysectomized rats. Since the factor remained after heating at pH 5.5 or pH 9 but was destroyed at pH 1 and pH 13 and since it was nondialyzable yet digested by pepsin, trypsin and chymotrypsin, it was concluded that erythropoietin is probably a polypeptide. In the presence of the non-precipitable proteins (by heat) of plasma, it is fairly stable to mild oxidation and reduction.
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