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Expression of transcription factors binding to the activating protein-1 (AP-1) site is induced by estrogens in association with epithelial proliferation in the uterus, but, in the oviduct, the relationship between cell proliferation and differentiation and AP-1 transcription factors is not well understood. In the developing rat oviduct, we found that proliferation and differentiation of epithelial cells were region-dependently regulated by 17beta-estradiol (E2). To determine the role of AP-1 transcription factors in the development of rat oviduct, we performed immunohistochemistry for epithelial c-jun and c-fos proteins in E2-untreated and -treated newborn rats. E2 increased the expression of c-jun and c-fos during proliferation of undifferentiated epithelial cells, but diminished both proteins during accelerated differentiation of ciliated epithelial cells. A pure estrogen receptor (ER) antagonist, ICI 182,780, inhibited changes in their expression during both cell proliferation and differentiation. Importantly, no reduction of c-jun was noted in the epithelial cells of the foxj1-deficient oviduct, which lacks cilia development. This study shows that c-jun and c-fos are regulated during epithelial cell proliferation and differentiation in a region-specific manner. This provides critical information for understanding the molecular and cellular mechanisms of the development of the neonatal oviduct.

To evaluate mechanisms of cell proliferation in the fetal female rat reproductive tract, diethylstilbestrol (DES) effects on cell division and estrogen receptor (ER), epidermal growth factor (EGF) and EGF receptor (EGF-R) expressions were determined from gestational day (GD) 15.5 to 21.5. Reproductive tracts were evaluated within three regions along the Mullerian duct axis; these were proximal, middle and caudal, which differentiate into oviduct, uterus and upper vagina respectively. In fetuses from non-treated dams, epithelial and mesenchymal proliferation, as evaluated by 5-bromo-2'-deoxyuridine incorporation, was decreased with development in all regions of the Mullerian duct. EGF levels were determined by immunohistochemistry. Mullerian epithelial EGF immunoreactivity was intense in the proximal and middle regions on GDs 15.5 and 17.5. EGF staining remained intense only in the proximal epithelia by GD 19.5 and was weak in the caudal epithelium, but substantially reduced throughout epithelia in all regions by GD 21.5. Thus, decreased cell proliferation correlated with decreased EGF expression in the developing Mullerian duct. DES (100 microg/kg body weight) was injected from GD 15 to 19 and female fetuses were collected on GD 19.5. DES increased Mullerian duct cell proliferation in the proximal epithelium and mesenchyme but decreased it in the caudal epithelium compared with oil-treated controls. No proliferative DES effect was observed in any cell type in the middle region. Mullerian duct EGF immunoreactivity was suppressed by DES compared with oil. Competitive RT-PCR indicated DES also decreased mRNAs for EGF, ERbeta1 and ERbeta2, but not ERalpha and EGF-R. These results indicate EGF may be an important regulatory factor of Mullerian duct cell proliferation, and that DES may alter cell proliferation by disrupting normal EGF, ERbeta1 and ERbeta2 expression in the developing female rat reproductive tract.