Placental hormones: I. Immunofluorescence studies of the localization of chorionic gonadotrophin, placental lactogen and prolactin in human and rat placenta and in the endometrium of pregnant rats.

Chorionic gonadotrophin (CG), placental lactogen (PL) and prolactin (PRL) were localized in sections of human and rat placenta using the indirect immunofluorescence technique. Antisera were absorbed with homologous and unrelated antigens by affinity chromatography or complexed with their respective antigens. To exclude binding of IgG and immune complexes to Fc-receptor in chorionic tissue, thus leading to erroneous results, sections were preincubated with an excess of rat IgG. The results indicate that, in the human placenta, human CG (hCG) and human PL (hPL) can be identified in the syncytiotrophoblast. Using antibodies to hPRL fluorescence was found in giant cells within the cytotrophoblastic islands in the intervillous space and in cytotrophoblastic cells within placental septa. In the rat placenta rat PL (rPL) and rat PRL (rPRL) could be identified in the giant cells of the basal zone. Furthermore rPRL/rPL was localized in the endometrium and adjacent decidial cells of rat pregnancy. No staining of chorionic cells was detected using antibodies against hCG and bLH, which cross-reacted with rLH. These experiments provide further evidence that the rat placenta is unlikely to produce a CG/LH-like hormone.