Two forms of decidualization-associated protein and their physicochemical relationship with acute-phase alphamacrofetoprotein in rats.

After isolation and purification, rat acute-phase protein, alphamacrofetoprotein and the uterine decidual protein, decidualization-associated protein were compared. They are similar in molecular weight and amino acid composition, and behave similarly during native polyacrylamide gel electrophoresis and are crossreactive with polyclonal antisera. They differ in pI values: with a mean pI of 4.83 for alphamacrofetoprotein, 5.16 for the major form of decidualization-associated protein and 4.97 for the remainder. Alphamacrofetoprotein and decidualization-associated protein differ in carbohydrate content and subunit structure, but show similar susceptibility to trypsin digestion. Evidence is provided that both the decidual species form complexes with proteases and that these are present in the extracted decidual proteins. The distribution of the forms of decidualization-associated protein in the tissues during pregnancy and parturition is described and discussed.