Identification of uterine nuclear type II estrogen binding sites in estrogen treated rats

Low content of estrogen receptors in human giant cell tumors of bone

We tried to identify estrogen receptors (ERs) in human giant cell tumors of bone. Samples from eight patients were used for biochemical and immunohistochemical studies using [125I]17 beta-estradiol and monoclonal antibody against the human ER. Estradiol binding sites were detected in seven cases out of eight. The dissociation constant of the higher affinity binding site was 0.5 nM. Nonlabeled 17 beta-estradiol and synthetic estrogen, diethyl-stilbestrol, inhibited the binding of labeled 17 beta-estradiol to the tumor cytosol, while dexamethasone did not inhibit the binding. Using a monoclonal antibody. Western blotting identified bands of M(r) 68,000 and 59,000. No ERs were observed in any case examined immunohistochemically. These results suggest that human giant cell tumors of bone have a low level of ERs that cannot be detected immunohistochemically.

Bone endothelial cells as estrogen targets

In the present study, we investigated the effects of estrogens on bone endothelial cell metabolism and the presence of estrogen binding sites in the same cells. For these studies, we have used a continuous cell line of clonal bovine bone endothelial cells for evidence of a direct response to estrogens in vitro. Receptor analysis to intact viable cells was steroid specific and saturable, with an apparent dissociation constant of 17.2 nM and a Bmax of 3.2 x 10(4) sites/cell. Northern blot analysis revealed a 6.5-kilobase mRNA that hybridized with a cDNA to human estrogen receptor. The 6.5-kilobase size is in close agreement with the reported size of the human estrogen receptor mRNA. In vitro estrogen responses of bone endothelial cells included a stimulation of cell proliferation as well as an inhibition of parathyroid hormone responsiveness. These findings clearly demonstrate the presence of functional estrogen receptors in bone endothelial cells in vitro, suggesting a role of estrogens in bone angiogenesis and in the entire process of bone remodeling.

In vitro effects of cytosolic inhibitor and opiates on the binding of [3H]oestradiol to nuclear type II binding sites of rat uterus and hypothalamus

The effect of cytosolic ultrafiltrates prepared from intact rat uteri, brain hemispheres and hypothalami and of some opiate analogues on oestradiol binding to nuclear type II sites in rat uterus and hypothalamus was studied. Opiate binding in nuclear fraction of rat uteri was also evaluated. Both uterine and hypothalamic low affinity nuclear oestradiol binding was inhibited by filtrate from uteri, while only hypothalamic nuclear binding was decreased in presence of hypothalamic filtrate. Filtrate from brain was ineffective on nuclear oestradiol binding of the studied tissues. Concentration dependent inhibition of uterine nuclear oestradiol binding could be demonstrated by some opiate analogues in vitro. Specific low affinity nuclear binding of opiate antagonist naloxone and agonist dihydromorphine was observed in rat uteri which could be inhibited by uterine filtrate and oestradiol but not by hypothalamic filtrate or other steroids. Present findings support the probable intracellular interplay of opiates and oestradiol action and suggest that cytosolic inhibitor factor might be involved.