Number Of Estrogen Binding Sites Research Articles

Effect of age on physico-chemical properties of the uterine nuclear estrogen receptors of albino rats

Estrogen receptors (ER) were extracted with high ionic strength buffer from the nuclei of uteri of young (21 weeks) and old (89 weeks) rats. Following the analysis of these receptors on a sucrose gradient and a Sephadex column, two peaks representing the two forms of receptors were obtained. The minor peak sedimented at 6.8 S with Stokes radius ( R S) = 7.2 nm, molecular weight ( M r) = 204 K and frictional ratio ( f f 0 ) = 1.71 . On the other hand, the major peak sedimented at 4.1 S with R S = 3.3 nm, M r = 57 K and f f 0 = 1.18 . These properties of nuclear ER were similar in both ages. Also, the half life of ER complexes from both ages at 25°C and 37°C were 135 min and 30 min, respectively. However, these complexes were retained for longer periods in the nuclei of young than old rats. Furthermore, the dissociation constant of the binding of nuclear receptors to estrogen remained constant, but the number of binding sites decreased from 1.56 in young to 1.05 pmol/mg DNA in the old. In young rats, about 61% of nuclear receptors bound to DNA-cellulose. Out of this 2 5 was eluted with 0.15 M and the remaining 3 5 with 0.5 M KCl. On contrary, only 37% of total receptors bound to DNA-cellulose in the old. Out of this 3 5 was eluted with 0.15 M and the remaining 2 5 with 0.5 M KCl. These data suggested that despite the similarity in different physicochemical properties, the number of estrogen binding sites and the retention time of ER complexes in nuclei and the ability of these complexes to bind to DNA decrease in the uterus of old age.

Differential Distribution of An Estrogen Receptor in the Submandibular and Parotid Salivary Glands of Female Rats

The purpose of this study was to measure the availability of the estrogen receptor in submandibular and parotid salivary glands in female rats. The presence of a specific, competitive, and saturable estrogen binder in rat salivary gland tissue was determined by saturation analysis and steroid competition in cell-free homogenates of salivary gland tissue from adult ovariectomized females. Scatchard analysis of the data indicated an estrogen receptor content of 1971.1 +/- 651.4 femtomoles/gm of tissue in submandibular salivary gland. This was significantly (p less than 0.01) greater than the number of estrogen binding sites in the parotid gland (457.1 +/- 123.4 femtomoles/gm tissue). Thus, there is a differential distribution in estrogen receptor content between parotid and submandibular salivary glands. The presence of an estrogen receptor in salivary gland tissue may serve to promote gender differences in submandibular salivary gland EGF content, to mediate changes in saliva composition during the female reproductive cycle and to regulate EGF release for cyclic uterine growth.

Bethanechol-induced increase in hypothalamic estrogen receptor binding in female rats is related to capacity for estrogen-dependent reproductive behavior

Neuroactive agents associated with different neurotransmitter systems can modulate the number of hypothalamic estrogen binding sites. It has been demonstrated previously that the muscarinic cholinergic agonist, bethanecol, administered 30 min prior to in vitro estrogen receptor assays increases the concentration of hypothalamic estrogen binding sites by 30–35% in female rats. Bethanechol was without effect on male hypothalamic preparations. In order to investigate further this sex difference and in an attempt to determine a relationship between the modulation of estrogen binding sites and a sexually differentiated function, bethanechol was given to female rats rendered either anovulatory and capable of displaying lordosis or anovulatory and behaviorally insensitive to estrogen. The results showed that bethanechol significantly increased the number of estrogen binding sites in females capable of displaying lordosis but not in females which did not show this estrogen-dependent behavior. It is possible that the capacity for drug-induced modulation of estrogen binding sites could be related functionally to the ability to display lordosis behavior.

Androgenic Regulation of Estrogenic Action on Accessory Sex Organ Smooth Muscle

AbstractOur previous research has shown that 4 weeks of daily estrogen treatment, started on the day of castration, resulted in significant growth of the guinea pig seminal vesicle smooth muscle, yet little or no estrogenic effect on muscle tissue weight or DNA content was observed when the treatment was initiated after a 1-month period of castration induced regression. With the hypothesis that castration induced reductions in estrogenic sensitivity were due to alterations in the intracellular fate of estradiol in the muscle, we determined, following the intravenous injection of 3H-estradiol to normal, 24-hour castrates and 1-month castrates, the whole muscle tissue accumulation and subcellular distribution of 3H-estradiol. In the same 3 experimental groups, we also determined, using in vitro exchange assays with 3H-estradiol, the number of estrogen binding sites in both the cytosol and salt (1.2m KCl) soluble fraction of the crude nuclear-myofibrillar pellet. It was found that the loss of estrogenic sensitivity in the 1-month castrate was not due to a reduction in either whole tissue accumulation, subcellular distribution, cytosol binding or salt-soluble nuclear binding of 3H-estradiol.Restoration of estrogenic responses in muscle DNA content and wet weight was achieved by priming 1-month castrates with 5 daily injections of dihydrotestosterone immediately prior to the onset of estrogen treatment. Shorter periods of androgen priming (e.g., 1, 2 or 3 days) slightly enhanced, but did not completely restore, estrogenic responses in muscle wet weight and DNA content. For estrogen sensitive parameters of muscle growth, such as collagen and RNA content, which were not altered in their response to the estrogen treatment by a 1-month period of castration-induced regression, androgen priming prior to estrogen treatment had no effect.Therefore, testicular androgens regulate selected facets of estrogenic sensitivity in guinea pig seminal vesicle smooth muscle; changes in the muscle cytosol or salt-soluble nuclear myofibrillar estrophiles do not appear to be responsible for the changes in estrogenic sensitivity.

Cytoplasmic estrogen receptors of rat mammary glands during pregnancy and puerperium.

The variation of cytoplasmic estrogen receptor in the mammary gland during pregnancy and puerperium was studied to determine the role of estrogens in the mechanism of lactation. Cytosol estrogen receptors from rat mammary glands were incubated with 3H-estradiol, and the free estradiol was removed using dextran-coated charcoal. The maximum number of binding sites in the cytosol was estimated from saturation curves and Scatchard analysis. During pregnancy the number of binding sites was relatively low (2.5 to 3.8 pmoles per mg protein), but increased after delivery to 7.8 pmoles per mg protein. The number of estrogen binding sites in the mammary glands of lactating rats five days after delivery was at the same level as on the day of delivery. However, at ten days after delivery the number of binding sites increased markedly to 58.9 pmoles per protein. The number of estrogen-binding sites in the mammary glands of lactating rats was decreased by castration and by the injection of testosterone or 2-bromoergocriptine. There appeared no competition by testosterone, progesterone or cortisol with estrogen receptors in the mammary gland.

Estradiol receptors in the pituitary and anterior hypothalamus of the rat: Measurement by agar gel electrophoresis

Agar gel electrophoresis has been applied to the measurement of the high-affinity saturable estrogen binding component in the cytosol of rat pituitary and anterior hypothalamus. Under the conditions employed, the number of available binding sites can be determined in small samples with good precision and accuracy. The total number of estrogen binding sites in the anterior hypothalamus of 28-day-old females was measurably (⋍15%) greater than that in males. A significant difference in the pituitary could not be demonstrated. The total number of binding sites in the pituitary was twice that in the anterior hypothalamus in both males and females.

Ontogeny of the estrogen receptor during early uterine development.

The number of estrogen binding sites in uterine cytoplasm on a per cell basis reaches a maximum by day 10 of life in both intact and castrate female rats. After this peak is reached, the number of binding sites per cell decreases, and the ratio remains constant until days 22 to 23 of life. Thus, the ontogeny of the estrogen binding protein is not dependent upon estrogen from the ovary and is probably an autonomous property of uterine cells. Sedimentation values and dissociation constants of the protein when the animals are 5 to 10 days of age are similar to those of the 22-day-old animal, indicating that the same protein is present throughout postnatal development.

Macromolecular Binding of Estradiol in the Rabbit Oviduct and Uterus

Macromolecular binding of estradiol in the ampullary and isthmic portions of the rabbit oviduct and the rabbit uterus was examined by <i>in vivo</i> uptake studies, sucrose gradient centrifugation, and binding assays. The studies revealed that the <i>in vivo</i> uptake was similar in the 3 mullerian areas examined. In addition, the estrogen receptor complex from all 3 areas had almost identical sedimentation characteristics in sucrose gradient centrifugation. Finally, the binding assays revealed that the number of estrogen-binding sites and the dissociation constants were similar in the 3 areas studied. These results indicate that the initial interaction of estrogen with the uterus and both portions of the oviduct is identical.