Localization of prolactin and its receptor messenger RNA in the human decidua

Prolactin (PRL) is known as an anterior pituitary hormone. On the other hand, PRL is also produced in the human decidualized endometrium. The physiological role and site of action of endometrial PRL have not yet been clarified. This study was designed to investigate the localization of PRL receptor (PRL-R) gene-expressing cells in the human decidualized endometrium using in situ hybridization histochemistry. Sense and antisense 35S-labeled RNA probes for human PRL-R mRNA were hybridized with cryostat sections of human decidua, which were obtained from patients undergoing therapeutic abortion at 8-10 weeks of gestation. Hybridization signals for PRL-R mRNA were seen over the decidual cells. No labeled cells were seen in the chorion, amnion, or trophoblast. Comparing the localization of PRL-R gene-expressing cells to that of PRL gene-expressing cells using adjacent sections, their distributions were quite similar. These results indicate that not only PRL but also PRL-R transcripts are located in the decidual cells.