Inhibition of progesterone receptor activity in yeast by synthetic chemicals

Numerous synthetic chemicals have estrogenic activity by interacting with the estrogen receptor. In this report, we test the hypothesis that some estrogenic chemicals may also modulate the human progesterone receptor (hPR) signaling pathway. This was evaluated by examining synthetic chemicals for their ability to modulate the activity of hPR expressed in yeast. The transcriptional activity of hPR was not increased in the presence of several synthetic chemicals. However, the estrogenic chemicals p-nonylphenol and 4-tert-octyphenol, and pentachlorophenol, effectively inhibited the activity of the hPR in yeast. Competition binding studies indicated these chemicals effectively competed with radiolabeled R5020, a synthetic progestin, for binding to the hPR in yeast. These results indicate that some synthetic chemicals directly inhibit the activity of hPR in yeast. The observations that some estrogenic chemicals can also inhibit hPR activity suggest a potential mechanism for the reported potent estrogenic activities of these chemicals.