[Tumor and fetus associated proteins--with special reference to alpha-proteins isolated and purified from rat placenta].

High molecular alpha-protein was isolated from rat placenta and purified with ammonium sulfate fraction and by DEAE cellulose column chromatography and Sephadex G-200 column chromatography, its physicochemical properties were elucidated. The serum alpha-protein levels were determined in pregnant rats, neonatal rats and tumor bearing rats according to single radial immunodiffusion. This protein was found to have a molecular weight of 750,000, an isoelectric point of 4.9 and E 1%1cm (280nm) of 9.0, showing mobility at position alpha 2 on immunoelectrophoresis. A small amount (24 +/- 8 micrograms/ml) was found in the serum of normal adult rat. In pregnant rats the serum level began to increase on the 10th day of pregnancy, reached its maximum (524 +/- 194 micrograms/ml) on the day of delivery, and thereafter gradually decreased. In neonatal rats the serum level reached its maximum (2104 +/- 446 micrograms/ml) on the 1st day after birth and thereafter gradually decreased. In the fetus the serum level was 3 to 4 times higher than that of the maternal rat. The protein levels were increased in the serum and ascites of some tumor bearing rats. These results suggest that this protein is related to the tumor and fetus.