EXPRESSION OF PROLACTIN GENE IN HUMAN DECIDUA DURING PREGNANCY STUDIED BY IN-SITU HYBRIDIZATION HISTOCHEMISTRY

The prolactin (PRL) gene is known to be expressed not only in the ante rior pituitary but also in the decidualized human endometrium. This st udy was designed to detect the site of synthesis of PRL during pregnan cy by in situ hybridization histochemistry. Decidual and trophoblast t issues from early pregnancy were obtained from patients undergoing the rapeutic abortion at 8-10 weeks of gestation. Term placentae were obta ined from patients with uncomplicated deliveries at 38-40 weeks. Secti ons of these tissues were hybridized with S-35-labeled RNA probe compl ementary to human PRL mRNA. Specific hybridization signals were distri buted over the decidual cells in early and term pregnancy. In the deci dua capsularis of early pregnancy, labeled cells were concentrated clo se to the amniotic cavity, although decidual cells were distributed ev enly. In the decidua parietalis, almost all decidual cells were labele d, but no specific labeling was seen in the endometrial glands or capi llary endothelium. In the decidua basalis, greater signals were always detected over the decidual cells in early pregnancy than in term preg nancy, when sections, which were hybridized with the same probe and ex posed simultaneously, were compared. No specific hybridization was det ected in the trophoblast cells. These results not only confirm that PR L is specifically synthesized in the decidual cells but also indicate that there are regional and periodical differences in PRL gene express ion in the decidual cells during pregnancy.