Progesterone receptor levels and distribution in different phases of the menstrual cycle and in estrogen-primed postmenopausal endometrium.

Progesterone receptor levels were measured in the cytosol and in the 0.4 M KCl nuclear extract of normal cyclic endometria in 49 women, classified into four categories: proliferative, midcycle, secretory, and estrogen-primed (four to 11 days); [3H]R5020 was used as a ligand. The women in each category were further subdivided into test and control groups; the women in the test group received a progesterone injection one to three hours before tissue collection. Both the nuclear progesterone receptor levels and the portion of the progesterone receptor in the nuclear extract were significantly higher in the test than in the control groups; among the test groups in the four categories, however, these changes were significantly smaller in women in the secretory category than in the other three categories. These results indicate that the progesterone receptor activation-translocation dynamics in human endometrium are dependent upon the hormonal status of the woman.