Placental lactogen-like proteins in the rabbit placenta.

Rabbit placentae and embryos at days 11 and 12 were analyzed by two-dimensional gel electrophoresis and by light microscopic histology for the presence of placental lactogen-like proteins. Immunoblotting and immunohistochemistry were performed by using a goat anti-human placental lactogen serum as well as a monoclonal mouse anti-human prolactin immunoglobulin; the results were similar. In the gel electrophoresis of placental tissue, three protein spots at pH 5.6 and 43, 39, and 35 kDa were immunostained; they were absent in the embryo. Immunoresponse was restricted to the cytotrophoblast. Immunofluorescent cells were mainly found on the proximal parts of the placental trabeculae.