IMMUNOCHEMICAL IDENTITY OF DECIDUALIZATION-ASSOCIATED PROTEIN AND ALPHA-2-ACUTE-PHASE MACROGLOBULIN IN THE PREGNANT RAT

'Decidualization-associated protein' (DAP), synthesized during deciduoma morphogenesis and pregnancy by the rat uterus, has been partially purified from decidual tissue by gel filtration and ion-exchange chromatography. DAP isolated by this method was suitable for use as an antigen and as a reference standard in rocket immunoelectrophoresis. The characteristics of an anti-DAP serum raised in rabbits are described. A radio-immunoprecipitation assay demonstrated that the uterus is the sole site of synthesis during early pregnancy and verified the tissue distribution of DAP synthesis previously detected using a polyacrylamide gel electrophoretic method. Employing rocket immunoelectrophoresis, DAP was detected in maternal serum from Day 9 of pregnancy. Serum levels increased until Day 13 and after remaining relatively constant increased further at parturition. In both neonates and post-partum animals serum levels fell at similar rates. In deciduoma-bearing pseudopregnant animals DAP was detected in the serum from 24 h after decidual induction. The contradictory observation that DAP was present in serum of animals where no apparent synthesis occurred was explicable by the finding that DAP was identical to α2 acute-phase macroglobulin (α2MG) as assessed by immunochemical techniques. This immunochemical identity was observed with both anti-DAP and anti-α2MG sera. These results are discussed in relation to the possible complete biochemical identity of DAP and α2MG, and to decidual tissue as an alternative site of α2MG synthesis in pregnancy. © 1979.