Steroid-hormone-binding proteins in normal and neoplastic mammary tissues from C3H mice fed diethylstilbestrol

Mammary tumors develop earlier and in greater numbers in C3H mice fed diets containing up to 1000 ppb diethylstilbestrol or 5000 ppb estradiol-17 beta. We have analyzed the steroid-hormone-binding proteins in cytosols of normal target tissues and in neoplastic mammary tissues of control and estrogen-fed mice to determine whether the capacity for hormone response was altered by dietary estrogens. Using estradiol-17 beta as a ligand, estrogen-binding proteins were measured with Kd = 10(-11)-10(-10) M and sedimentation constants of 8 and 4 S. The binding capacity (per mg cytosol protein) of uterus exceeded that of normal mammary gland 10-20-fold, while mammary tumors only contained half the binding capacity of virgin mammary gland. Binding proteins for the glucocorticoid, triamcinolone acetonide, exhibited a sedimentation constant of 7-8 S and Kd = 10(-9)-10(-8) M. The glucocorticoid binding capacity of mammary tumors exceeded that of virgin mammary gland. Binding proteins for progestins were measured using the synthetic ligand R5020. Mammary gland contained progestin-binding proteins with 4 S sedimentation constants and Kd = 10(-9)-10(-8) M. Not all mammary tumors contained progestin-binding proteins, and the binding capacities varied considerably among those that did. The molecular characteristics of the steroid receptors in tumors were the same as those found in normal target tissues. There was nothing to suggest that dietary estrogens altered the characteristics of the three steroid-binding proteins.