Immunofluorescent localization of ovine placental lactogen

The localization of ovine placental lactogen (OPL) was studied using the immunofluorescence method. The placentome sections were treated by an indirect technique with anti-OPL antibodies obtained from rabbits injected with purified hormone. OPL was located in large cells of the monostratified epithelium of chorionic villi. These cells are mono- or binucleated and PAS-positive. The immunological reaction was inhibited by the specific antigen (OPL, 400 microgram/ml undiluted anti-OPL antiserum) but not by ovine prolactin, bovine growth hormone, human placental lactogen nor by any other polypeptidic hormone tested. Reciprocally, the localization of OPL-secreting cells was unsuccessful with antibodies raised against these control hormones.