Studies on the Antiprogesteronge and the Anti-glucocorticoid Activity of Mifepristone

Objective:To analyse the binding affinities to progesterone and glucocorticoid re-ceptorsof themifepristone. Methods:With radioligand binding assay, the receptor binding affinityof mifepristone to the rabbit uterus cytosol progesterone receptor and the rat liver glucocorticoid re-ceptor were measured. Results:Compared with progesterone, the relative binding affinity of mi-fepristone is396.67±25.32, and the 50% inhibitory concentration is (6.61±1.20) nmol/L; Comparedwith dexamethasone, the relative binding affinity of mifepristone is 344.41 ± 57.41, and the 50%inhibitory concentration is ( 4.21±1.02) n mol/L. Conclusion:Mifepristone, as a strong agent ofantiprogestin, can block progesterone and glucocorticoid activitiesand the anti-glucocorticoid effectof mifepristone should be noticed enough in the clinical use of this drug.