[The comparison of the binding of Ru486 to progesterone receptor of pituitary and endometrium in ovariectomized rat].

Following intramuscular injections of increasing doses of Ru486 (0.1 mg/kg-2 mg/kg), free progesterone binding sites remaining in pituitary and endometrium in estrogen-primed OVX rats decreased. Thirty minutes after administration of Ru486 (2 mg/kg) the binding sites of progesterone receptor in both tissues showed a significant initial decrease, and then gradually reached the lowest level in 2 h. Afterwards the levels of progesterone receptor began to increase. The results suggested that Ru486 could interact with progesterone receptor in both tissues. However, the binding ability of Ru486 for different tissue was not exactly the same, and Ru486 binding to the progesterone receptor in endometrium might be easier.