Dynamics of estrogen binding by uterine cells in vivo

The dynamics of the in vivo binding and release of tritiated estradiol in different uterine cell types are described. The very early binding of estrogens by the cytosol-nuclear and the eosinophil receptor systems is in accordance with the hypothesis that some estrogenic effects are mediated by these receptor systems.     

Effect of Progesterone on the in vivo binding of estrogens by uterine cells

Summary Progesterone selectively inhibits estradiol upltake by the nuclei of the luminal epithelial cells but not by other uterine cells. This inhibition in estrogen binding parallels the inhibition by progesterone of some estrogenic responses in the luminal epithelial cells only.Acknowledgments. This work was supported by Grant No. 2015 From the Oficina Técnica de Desarrollo Cientifico y Creación Artística of the University of Chile.     

Effect of progesterone on the in vivo binding of estrogens by uterine cells.

Progesterone selectively inhibits estradiol uptake by the nuclei of the luminal epithelial cells but not by other uterine cells. This inhibition in estrogen binding parallels the inhibition by progesterone of some estrogenic responses in the luminal epithelial cells only.     

In vivo occupation of estrogen receptors by hydroxylated metabolites of tamoxifen]

We report that after in vivo administration of (3H) tamoxifen, the cytosol and nuclear estrogen receptor sites of Rat uterus and Chicken oviduct are mostly occupied by polar metabolites. One of the major metabolites is 4-hydroxy-tamoxifen which we have identified by cocrystallisation withe non radioactive compound and which is known to display a high affinity for the estrogen receptor. In the Rat uterus, the proportion of the metabolites versus tamoxifen, increases with time with a maximum at 8 hrs. for the 4-hydroxy-tamoxifen. Other hydroxylated metabolites (M2) became predominant after 24 hrs. We propose that in vivo, the synthetic antiestrogens act mostly via their transformation into hydroxylated metabolites.     

Characterization of the estrogen receptors in the uterine and blood eosinophil leukocytes

Summary Estrogen receptors are found in the rat uterine and in the eosinophil-rich human blood leukocyte 24,000g fractions, but not in the low-eosinophil count human blood leukocyte 24,000g fraction. The total number of binding sites per blood eosinophil leukocyte is 7,400 sites per cell, and theK _d =5.6×10^–10 M.Acknowledgments. This work was supported in part by funds from the Unité de Recherches sur le Métabolisme Moléculaire et la Physio-Pathologie des Stéroïdes de l'INSERM, Hôpital de Bicetre, France, and by grant No. 2015 from the Oficina Técnica de Desarrollo Científico y Creación Artística of the University of Chile.     

The kinetics of estrogen binding to rat alpha-fetoprotein

Fluid obtained from rat fetuses was utilized to characterize the affinity, number of binding sites, and the association and dissociation rate kinetics of the binding of estradiol and estrone to AFP. Statistical analysis demonstrated no differences when the values for the AFP-estradiol interaction were compared with those obtained for the ATP-estrone interaction. These data demonstrate that rat AFP specifically binds estradiol and estrone with a high capacity, high affinity, and similar binding kinetics.     

The kinetics of estrogen binding to rat α-fetoprotein

Summary Fluid obtained from rat fetuses was utilized to characterize the affinity, number of binding sites, and the association and dissociation rate kinetics of the binding of estradiol and estrone to AFP. Statistical analysis demonstrated no differences when the values for the AFP-estradiol interaction were compared with those obtained for the AFP-estrone interaction. These data demonstrate that rat AFP specifically binds estradiol and estrone with a high capacity, high affinity, and similar binding kinetics.This work was supported by NSF grant PCM-8109847 and by a Grant-in-Aid of Research from Sigma Xi, The Scientific Research Society.     

Specific in vivo binding of d-LSD in rat brain

A reproducible in vivo d-LSD binding method in rat brain is described, with high affinity (Kd of 5 pmoles/g wet wt), stereospecificity (d- vs. 1-LSD) and regional selectivity. It may be a useful adjunct to in vitro methods for measuring changes in turnover at the synaptic level related to the intact receptor.     

Specific in vivo binding of d-LSD in rat brain

Summary A reproducible in vivo d-LSD binding method in rat brain is described, with high affinity (K_d of 5 pmoles/g wet wt), stereospecificity (d-vs, vs. l-LSD) and regional selectivity. It may be a useful adjunct to in vitro methods for measuring changes in turnover at the synaptic level related to the intact receptor.     

Regulation of estrogen "receptors" in mammary tumors: action of prolactin in vivo

The effect of prolactin on estradiol receptors was determined in cytosol of estrogen-dependent mammary tumors of Sprague Dawley rats. Tumors were induced with 20 mg dimethylbenzanthracene, rats were ovariectomized, and the rats showing regression in tumor weight were given 1 mg sheep or rat prolactin for 5 days. Receptors were separated by dextran-charcoal and analyzed by sucrose gradient. Prolactin, milk proteins, serum proteins, and 1-alpha-feto-proteins were excluded immunologically. The estradiol receptors resembled uterine receptors in affinity, specificity, sedimentation, and nuclear transfer under estradiol influence. Castration diminished receptor content exponentially 170 f moles to 16 f moles/mg protein within 10 days; prolactin increased the number of receptors to 87 f moles compared with 15 in controls. Affinity, cellular location, and uterine receptor content were unaffected. Sheep and rat prolactin acted similarly. These results justify hypophysectomy as therapy for certain estrogen-dependent breast tumors.     

Bromocriptine and sulpiride competitively inhibit estrogen binding to its receptor in the adrenal gland

Bromocriptine and sulpiride incubated simultaneously with [3H]-estradiol in the cytosol from adrenal glands of adult male rats, yielded curves typical of competitive inhibition as analyzed by Lineweaver-Burk plots. The inhibition constant for both drugs was approximately 10(8) M-1, only 10 times lower than the association constant for estradiol.     

Actinomycin binding and uridine incorporation by human normal bone marrow cells

Riassunto Nel midollo umano normale, parallelamente alla differenziazione cellulare delle linee mieloide ed eritroide, si osserva, per l'incorporazione dell'uridina nell'ARN, una diminuzione maggiore di quella della fissazione dell'actinomicina-D alla cromatina.     

Cytoplasmic DNA of hepatoma tumor cells studied by3H-actinomycin D binding

Résumé L'ADN cytoplasmique d'hépatome fixe deux fois plus de³H-actinomycin D que le foie normal. Cette différence peut être expliquée soit par l'augmentation de l'ADN cytoplasmique du tumeur ou par l'augmentation de fixation de³H-actinomycin D à l'ADN du tumeur.