Estrogen binding in the rat uterus: heterogeneity of sites and relation to uterotrophic response
| Autor: | James W. Hardin, Susan Upchurch, Hakan Eriksson, James H. Clark, Barry M. Markaverich |
|---|---|
| Rok vydání: | 1980 |
| Předmět: |
medicine.medical_specialty
medicine.drug_class Estrogen receptor Biology Biochemistry Endocrinology Cytosol Internal medicine medicine Animals Castration Estrogen binding Receptor Cellular compartment Cell Nucleus Estradiol Uterus Ligand (biochemistry) Rats Kinetics Receptors Estrogen Estrogen Organ Specificity Ovariectomized rat Female Spleen |
| Zdroj: | Journal of steroid biochemistry. 12 |
| ISSN: | 0022-4731 |
| Popis: | Multiple species of estrogen binding sites have been demonstrated in cytosol and nuclear fractions of uterine cells from immature and adult ovariectomized rats. Cytosol . Type I sites show properties identical to the classical cytoplasmic estrogen receptor. Type II binding sites have lower affinity for the ligand, exist in higher concentrations and do not undergo nuclear translocation after estrogen stimulation. These secondary sites may be involved in the retention of estrogens within the uterus, by creating an estrogen rich environment for binding to type I sites which in turn translocate estrogen as a receptor-hormone complex to the nucleus. Since it is not known whether type II sites are intra- or extracellular, they may act in this buffer capacity in either or both cellular compartments. Another possibility is that type II sites are precursors of type I sites. Nucleus . In addition to type I sites, a second site was also observed in the nuclear compartment. This second nuclear binder does not appear to be related to the cytosol type II site; however they have similar dissociation constant and share hormone and tissue specificity. Estradiol administration causes an increase in both specific binding components in uterine nuclei of mature ovariectomized rats. The second component (type II) binds estradiol with a higher capacity than type I sites, and displays a saturation curve which is sigmoidal. The stimulation of type II sites is a specific estrogenic response and is highly correlated with uterine growth. A single injection of estradiol results in long term retention of type I sites (6h), rapid and sustained elevations of type II sites (1–72 h) and true uterine growth. In contrast, estriol injection caused a rapid increase in type I sites which was not accompanied by an increase in type II sites and no true uterine growth occurred. Conversely the administration of estriol by paraffin implant sustained elevated nuclear levels of type I sites, increased nuclear type II sites 2–3 fold above controls and stimulated true uterine growth 48 h following hormone administration. These data suggest that estrogen stimulation of true uterine growth may require long term (6–24 h) nuclear retention of type I sites and sustained elevation in type II sites. These secondary sites do not appear to be translocated to the nucleus but instead may be chromosomal proteins which are present in the nucleus of uterine cells at alt times. We conclude that elevated levels of nuclear type II sites correlate well with the biosynthetic events associated with the long term uterotrophic response to estrogenic hormones. |
| Databáze: | OpenAIRE |
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