Binding of bis-β-Chloroethylamine Derivatives of Synthetic Estrogens to Proteins: Dependence on the Chemical Structure

We studied binding of 10 new bis-β-chloroethylamine derivatives of synthetic estrogens of different chemical structure to estradiol receptors in cytosolic fraction of breast carcinoma tissue and to blood plasma proteins. 11α-Derivatives of estrone and ethynylestradiol with bis-β-chloroethylamine radical at the 3-position were most potent, while 11β-substances with the cytostatic residue in this position less effectively competed with labeled estradiol for estradiol receptors. Estrone derivatives with cytostatic residue at the 3-position bound primarily to serum albumin. Ethynylestradiol derivatives with cytostatic residue at the 3-position of the steroid nucleus bound to plasma globulins. Cytostatic radical at the 11-position changed spatial conformation of estrogen cytostatics and they lost their ability to interact with estradiol receptors and blood plasma proteins.