Effect Of Exogenous Estrogen Reagents On The Expression Of Estrogen Receptor α And β In Uterus Of SD Rats

Backgroud Endometrial cancer is the one of the three most common malignancies of the female reproductive organs. It mostly affected women in the postmenopausal age group. The development of endometrial cancer appears to be associated with the exposure to estrogen excess state over the long period time. Postmenopausal hormone replacement therapy (HRT), especially the use of unopposed estrogen, leads to increased endometrial cancer. The exact mechanism for estrogen's proliferation and its role in neoplasia remains unknown. Estrogen's cellular actions on the target organs are mediated via estrogen receptor (ER). Until recently, it was assumed there was only one form of ER. However, in 1995, a second ER, ER , was cloned from a rat prostate cDNA library. The classical ER is now referred to ER . The ER protein is highly homologous to ER , particularly in the DNA-binding and the ligand binding domains. ER 3 has been shown to act as a transcription factor and modulate the expression of target genes as ER .However, the two subtypes have different tissue distributions and relative levels, have different affinity for ligands and have different gene activations. The effects of the two subtypes are adverse sometimes. The changes of ERs expression levels may lead to different effects. Uterus is a major target organ of estrogen's actions. ER 3 is expressed in uterus as ER a , but its function in the uterus remains unknown. Some investigators hypothesized that ER 3 is a modulator of ER a in the uterus and some roles of estrogen are mediated through ER 3 . There are few studies about the changes of the two ERs in the uterus after menopause. Exogenous estrogen may influence the expression of ERs in the uterus, which maybe associated with the endometrial hyperplasia and the development of neoplasia. But few studies reported it and the results are not coincidence.Premarin and Progynova are the most common used estrogen reagents at present. To investigate the effects of the two reagents on the expression of ERs and endometrial proliferation has important clinical significance. Proliferating cell nuclear antigen (PCNA) is a useful and reliable index in the detection of cell proliferation.Objective The adult female Sprague-Dawley (SD) rats were used to explore the distributions of ERs in uterus and the expression changes of ER and ER in uterus following ovariectomy. Ovariectomized SD rats were used to study the regulation of ER and ER after treatment with two estrogen reagents, Progynova and Premarin. In addition, the levels of PCNA were measured in endometrium to clarify the relations of the expression of ERs and the ratio of ER /ER a and endometriual proliferation.Materials and Methods Forty adult female SD rats were divided into four groups: intact (control), ovariectomized (OVX), OVX+Progynova (Progynova), OVX+Premarin (Premarin). The uterus tissue of control group were collected at estrus without interferes. The rats in the other three groups were ovariectomized at estrus. The rats in the two experiments groups were orally injected with Progynova or Premarin for 12 days after they had been ovariectomized for 48 days. At the same time, the OVX group rats were orally injected with saline sodium as control. Tissue samples were collected, and reverse transcription polymerase clain reaction (RT-PCR) and Western blotting were employed to detect the expression of ER and ER in mRNA and protein levels in uteri. ERs mRNA and protein levels were compared by relative quantitative analysis. A streptavidin peroxidase conjugated (SP) immunohistochemistry assay was used in control group samples to determine the location of ERs protein in uterus. The levels of ERs in grandular epithelial cells, luminal epithelial cells, stromal cells of the endometrium and smooth muscle cells were analyzed by semi-quantitative H-Score assay. The expression of PCNA were measured in endometrium by SP immunohistochemistry and analyzed by PCNA-labeling index. The relations of PCNA-labeling index in grandular epithelial cells...