Plasma diethylstilboestrol binding proteins of rat, mouse and man in the course of development: relations with the binding of estradiol.

High diethylstilboestrol (DES) binding has been demonstrated in fetal and adult sera from man, rat and mouse by equilibrium dialysis and electrophoretic techniques. In the adults of the three species and in the human fetus only albumin shows an elevated binding capacity for DES. By contrast, in the case of rat and mouse embryos there are two proteins, namely albumin and alpha-fetoprotein, which afford major and quantatively similar contributions to the binding. Human alpha-fetoprotein does not bind DES. These phenomena are analysed in relation to the estrogen binding characteristics of the alpha-fetoproteins of the three species.