[Comparative study of the estrogenic activity of modified estrogens based on data of competitive binding analysis and...

A series of bromo- and silyl-derivatives was studied in experiments on immature female rats in vivo and in vitro. All the estrogens studied were conventionally divided into 4 groups according to their ability for concurrent binding with the rat uterus cytosol receptors and their specific bioeffect: equally concurrent and bioeffective compounds (estrone, ethynyl estradiol); slightly concurrent substances with a pronounced uterotropic action (4-silyl estrogens, mestranol); little effective compounds with 4 to 8% of estradiol concurrent activity (2- and 4-bromo-and silyl estradiols, estriol); compounds, not having concurrent and biological effects (2-silyl estrones, 4-bromoestradiol diacetate).