Effect of antibodies against distinctive rat liver estrogen-binding protein on hormone-binding activity of this protein and steroid hormone receptors

The effect of rabbit polyclonal antibodies (AB) against a distinctive estrogen-binding protein (DEBP) of rat liver, isolated using an immunosorbent, on the interaction of [3H]estradiol with the DEBP and estrogen receptors of the uterus and other tissues, as well as of [3H]dihydrotestosterone with prostate androgen receptors, [3H]progesterone with uterine progesterone receptors, and [3H]dexamethasone with rat thymus glucocorticoid receptors was investigated. It was found that preincubation of the cytosol of the tissues under investigation with the antibodies decreases the capacity of the DEBP of the estrogen and androgen receptors to bind the corresponding ligand. The hormone-binding activity of progesterone and the glucocorticoid receptors does not change in the presence of AB. The binding activity of DEBP in the presence of AB decreases as a result of a decrease in the concentration of binding sites of the protein, while that of the estrogen and androgen receptors drops as a result of a decrease in affinity for the ligand, due to a drop in the association rate constant. A cross effect of AB on the activity of uterine estrogen receptors of the rabbit, guinea pig, and mouse was found. It was concluded that there is a definite similarity in the structure of DEBP and sex steroid receptors