Immunological demonstration of alpha-fetoprotein in uterine cytosol from immature rats

An immunological demonstration of alpha-fetoprotein (AFP) in uterine cytosol from immature rats is reported. The identity between serum AFP and the estrogen binding 4.5 S macromolecular complex of uterine cytosol was demonstrated by the use of a specific immunoadsorbent to AFP. Analysis of the sedimentation profile in glycerol gradients of uterine cytosol incubated with tritiated estrone or estradiol suggests that the total estrogen binding capacity of the 4.5 S complex is provided by AFP. Changes of AFP content in rat uterus with the age of the animals suggest that this protein is probably present in the cytosol as a serum contaminant.