Evidence for progesterone receptors in the human fetoplacental vascular tree

The presence of progesterone receptors (PR) throughout the human term fetop lacental vascular tree was investigated, By reverse transcription-polymeras e chain reaction (RT-PCR), we showed expression of PR mRNAs in stem villi v essels, chorionic arteries and veins, and umbilical arteries and veins. Bin ding studies and Scatchard analysis revealed a single class of high-affinit y binding sites for H-3-R5020 (promegestone) in cytosolic extracts of all p lacental vessels, with K-d values in the range of 2.5-4 nM. High levels of PR were detected in placental vessels compared to other vascular tissues. T hus, maximum binding capacities of stem villi vessels, chorionic arteries a nd veins, and umbilical arteries and veins were 247 +/- 25, 377 +/- 58, 295 +/- 40, 371 +/- 118, and 672 +/- 144 fmol/mg protein, respectively. Endoth elial cell elimination in chorionic arteries did not significantly modify t he number of PR. RT-PCR and binding studies also assessed PR expression in cultured placental vascular smooth muscle cells isolated from stem villi ve ssels, All these data suggested that most of the PR of fetoplacental vessel s were from the media. In conclusion, we report here the first evidence of the presence of PR in t he muscular layer of human term fetoplacental vessels. This finding, togeth er with the high progesterone concentrations in cord blood, suggests that t he interactions between the PR and its ligand may play a role in the physio logy and physiopathology of human fetoplacental vascularization.