Expression of prolactin receptors in human osteosarcoma cells. The expression of prolactin receptor (PRL-R) mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) combined with Southern analysis in total RNA extracts from two human osteosarcoma cell lines (MG-63 and Saos-2). The level of PRL-R transcript was significantly enhanced in cells cultured in the presence of 1,25-(OH)2 vitaminD3 (10(-7)M) and to a lesser extent in the presence of dexamethasone (10(-6)M). This first demonstration of PRL-R gene expression in osteoblast-like cells supports the hypothesis of a direct action of prolactin in bone cells, which is further strongly suggested by the stimulatory effect of 1,25-(OH)2 vitaminD3 and dexamethasone on PRL-R mRNA level in these cells.