Immunohistochemical study on oxytocin-like substance in the human placenta.

Our previous studies have demonstrated that a large quantity of oxytocin (OT)-like substance exists in human placental tissue. In the present study, the localization of the OT-like substance in the human placenta was investigated by the PAP (peroxidase and antiperoxidase complex) immunohistochemical method. The results demonstrated that the site of syncytiotrophoblast was positively stained by specific antiserum to OT, whereas the tissue was not significantly stained by normal rabbit serum (NRS). These results suggest that the OT-like substance might be localized in syncytiotrophoblast of the placental tissue.