Detection of in situ localization of long form prolactin receptor messenger RNA in lactating rats by biotin-labeled riboprobe.

Biotinylated riboprobe that specifically hybridized with messenger RNAs (mRNAs) encoding the long form of prolactin receptor (PRLRL) was transcribed from 269 bp Hind III and Xho I fragment of the cytoplasmic domain of PRLRL complementary DNA (cDNA). The probe was used for in situ hybridization to identify tissue localization of PRLRL mRNA in the mammary gland, liver, ovaries and kidneys from lactating rats at 24-36 h after delivery. Histochemical detection of signals by means of horseradish peroxidase (HRP)-labeled streptavidin revealed that the PRLRL gene was expressed on the alveolar epithelial cells and mammary ductal epithelium in the mammary gland, and hepatocytes in the liver. In the ovary, the PRLRL gene was expressed on the luteal cells in the newly formed corpus luteum, granulosa cells and theca cells of follicles at various stages of development, hypertrophied theca cells in the atretic follicle, and secondary interstitial cells, but no signal was observed in the kidney. Biotinylated sense RNA probe did not detect any signals in any of the tissues examined. In situ hybridization with non-radiolabeled probe provided the identification of PRLRL mRNA in the fine tissues, such as follicular epithelium in the ovary, and showed the morphology of individual cells expressing the PRLRL gene. In particular, the diversity of signal intensity in the same mammary gland with different appearances suggested the existence of a local mechanism controlling PRLRL gene expression.