Progesterone receptor expression in the human placenta

The presence of progesterone receptors (PR) in the human placenta has been demonstrated using the reverse transcriptase-polymerase chain reaction tech nique. It was observed that the amount of PR in the human placenta is less during late gestation. Electrophoretic mobility shift assays with nuclear e xtract isolated from the first trimester and term placenta revealed three c omplexes when incubated with [P-32]dCTP-labelled progesterone response elem ent, and, in competition with unlabelled progesterone response element, the formation of all three complexes was inhibited. When supershift analysis o f these complexes was carried out using antibodies which cross-react with b oth the A and B types of the PR or only with the B type receptor, only the A-form of PR was detected in the human placenta.