Estrogen Receptors in Bone An Evaluation of the Uptake of Estrogen into Bone Cells

The uptake of 3H-estradiol-17β in bone cells was evaluated. Nuclear and cytoplasmic fractions were prepared from pulverized bone. Incubations were done in 3H-estradiol-17β and 3H-estradiol-17β plus tenfold unlabeled estradiol. Protein-bound estrogen was measured in cytosol, and nuclear radioactivity was measured per mg DNA. There was no difference in the radioactive/radioactive and unlabeled uptake. Because of the absence of specific binding, it is concluded that bone is not an estrogen receptor tissue in the classical sense and that the hormone's effect on osseous metabolism must be explained in other ways.