Effect of progesterone injection on progesterone receptor levels and distribution in untreated and short-term Premarin-primed pre-menopausal and post-menopausal endometrium.

Cytosolic and nuclear progesterone receptors (RPC, RPN) were measured in post-menopausal endometria, using [3H]R5020 as the radioligand, and the findings compared with those in pre-menopausal endometria. Total RP levels (RPC + RPN) in post-menopausal endometria were low, i.e. less than 2000 fmol/mg DNA. A 7-11 day course of Premarin (conjugated equine oestrogen) treatment in post-menopausal subjects resulted in RP levels in 11818 +/- 3008 fmol/mg DNA, which were higher than those in proliferative, mid-cycle and Premarin-primed pre-menopausal endometria. Progesterone injection 1-3 h before tissue collection resulted in a change in the distribution of the RP in both premenopausal and post-menopausal Premarin-primed endometria and pre-menopausal proliferative and mid-cycle endometria. Following the progesterone injection RPN levels increased to 57 +/- 9% of the total as compared with 23 +/- 8% in endometrial samples from women who received no progesterone.