Progesterone receptor in the human uterine cervix.

A progesterone receptor (PR) in human uterine cervical nuclei was demonstrated by a nuclear exchange assay using a synthetic progestin, promegestone (R5020) as a radio-labeled ligand. Total exchange of previously bound progesterone with R5020 was achieved by incubation at 0 degree C for 3 h. A 0.6 M KCl solution was used to extract the nuclear PR in uterine cervical tissue, and the dextran coated charcoal (DCC) method was used to separate the free [3H] R5020 from the bound form. Scatchard plots of nuclear PR binding showed two components with dissociation constants of Kd = 2.3 X 10(-10) and 4.6 X 10(-9) M. Three histological regions of the uterine cervix was studied as to their nuclear PR contents throughout the menstrual cycle. In the follicular phase, the connective tissue (CT) had the highest PR concentration (658.9 fmole/mg DNA), followed by the columnar epithelium (CE) (253.6 fmole/mg DNA), and the squamous epithelium (SE) (184.7 fmole/mg DNA). In the luteal phase, there was no significant difference among the three regions. Comparing these phases of cycle revealed that the CT had higher PR contents in the follicular phase than in the luteal phase, but no such difference was found in the CE or SE. These three regions had the same Kd value in both phases.