Аннотация:Alpha-fetoproteins (AFP) from amniotic fluid of mouse and rat demonstrate high affinity and specificity during their binding with immobilized diethylstilbestrol, which allows to isolate these two proteins by one step using the method of affinity chromatography on Sepharose with immobilized diethylstilbestrol. Meanwhile the yield of mouse AFP was 42%, and rat AFP--75%. The preliminary incubation of the amniotic fluid of rat and mouse with free estradiol results in abrupt fall of AFP outcome, which may testify to the binding of estradiol and diethylstilbestrol by the same receptor sites on AFP molecule.