Modulation of phosphorylation and dephosphorylation of keratin and other polypeptides by estradiol-17 beta in rat vaginal epithelium

Effects of tamoxifen on vaginal blood flow and epithelial morphology in the rat

Background

Tamoxifen, a selective estrogen receptor modulator with both estrogenic and anti-estrogenic activity, is widely used as adjuvant therapy in breast cancer patients. Treatment with tamoxifen is associated with sexual side effects, such as increased vaginal dryness and pain/discomfort during sexual activity. There have been limited investigations of the effect of tamoxifen on estrogen-dependent peripheral genital arousal responses. The objective of this study was to investigate the effects of tamoxifen on vaginal physiology in the rat.

Methods

Female Sprague-Dawley rats were subjected to sham surgery or bilateral ovariectomy. After 2 weeks, sham-operated rats were implanted with subcutaneous osmotic infusion pumps containing vehicle (control) or tamoxifen (150 μg/day). Ovariectomized rats were similarly infused with vehicle. After an additional 2 weeks, vaginal blood flow responses to pelvic nerve stimulation were measured by laser Doppler flowmetry and vaginal tissue was collected for histological and biochemical assay.

Results

Tamoxifen treatment did not change plasma estradiol concentrations relative to control animals, while ovariectomized rats exhibited a 60% decrease in plasma estradiol. Tamoxifen treatment caused a significant decrease in mean uterine weight, but did not alter mean vaginal weight. Vaginal blood flow was significantly decreased in tamoxifen-infused rats compared to controls. Similar to ovariectomized animals, estrogen receptor binding was increased and arginase enzyme activity was decreased in tamoxifen-infused rats. However, different from control and ovariectomized animals, the vaginal epithelium in tamoxifen-infused rats appeared highly mucified. Periodic acid-Schiff staining confirmed a greater production of carbohydrate-rich compounds (e.g. mucin, glycogen) by the vaginal epithelium of tamoxifen-infused rats.

Conclusion

The observations suggest that tamoxifen exerts both anti-estrogenic and pro-estrogenic effects in the vagina. These physiological alterations may eventually lead to vaginal atrophy and compromise sexual function.

Sex hormone receptors in the human eye

Dissimilarities in ocular physiopathology exist between human males and females. These differences can be observed in the lacrimal and other eye-associated glands, the ocular surface, the crystalline lens, and the retinochoroid complexes. Literature on the subject revealed that because of sex steroid hormone (estrogen, progesterone, and androgen) actions, various physiological conditions, such as age, menstrual cycles, pregnancy, and menopause or andropause, where the hormone milieu changes, affect vision. Well-designed scientific studies are lacking on the subject, although such studies hold much potential value. This review analyzes the relatively new area of hormones and vision.

Conventional estrogen receptors are found in the plasma membrane of vaginal epithelial cells of the rat

Estrogens induce rapid (non-genomic) and delayed (genomic) effects on the target cells. The early effects include induction of signal transduction pathway within seconds, whereas the delayed responses require hours and involve transcription and translation. The rapid effects of estradiol (E) on the vaginal epithelial cells (VEC) involved calcium uptake within seconds via the induction of phosphoinositol lipid metabolism as reported in our earlier studies. In this study, we demonstrate the presence of classical estrogen receptors (ER) on the plasma membrane of VEC of the rats. Immunoreactive bands of 67, 56 and 35 kDa are detectable in the membrane fractions (mf) using antibodies recognizing different epitopes of ER alpha. We have also been able to purify a protein having a mass of 67 kDa from the detergent-soluble fraction of the plasma membrane of VEC, which shows properties identical to the classical receptor purified from the cytosolic fraction of the cells. The membrane receptors get dissociated upon binding to the ligand. Besides a role in signal transduction events induced by estradiol, the membrane estrogen receptors may have an important role to play in translocation of the steroid to the cytosolic compartment.

Estrogen-induced epithelial proliferation and cornification are uncoupled in sinus vaginal epithelium associated with uterine stroma

Epithelium from the urogenital sinus-derived portion of the newborn mouse vagina when grown in association with uterine mesenchyme forms a "vaginal" stratified squamous non-cornified epithelium. However, the epithelium of these tissue recombinants composed of sinus vaginal epithelium plus uterine mesenchyme does not undergo the fluctuations in cytodifferentiation normally seen in vaginal epithelium during the estrous cycle (e.g., cornification and mucification). In this report we show that sinus vaginal epithelium in association with uterine mesenchyme proliferated in response to estradiol but failed to cornify in response to diethylstilbestrol (DES), even though both the epithelium and the stroma had estrogen receptors. However, if sinus vaginal epithelium that had been grown in combination with uterine mesenchyme was re-isolated from the tissue recombinant and recombined with fresh vaginal mesenchyme, the epithelium cornified in response to DES. These results indicate that the proliferative and the cytodifferentiation response to estrogen could be uncoupled and that sinus vaginal epithelium required vaginal stroma to cornify in response to DES.