Effect of diethylstilbestrol on cell proliferation and expression of epidermal growth factor in the developing female rat reproductive tract 

Journal of Endocrinology v.170, i.3 Sep01

A Okada, T Sato¹, Y Ohta², D L Buchanan^3,4 and T Iguchi^3,4

Safety Research Laboratories, Yamanouchi Pharmaceutical Co., Ltd, Itabashi, Tokyo 174-8511, Japan
¹Graduate School of Integrated Science, Yokohama City University, Yokohama, Kanagawa 236-0027, Japan
²Laboratory of Animal Science, Department of Veterinary Science, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan
³Center for Integrative Bioscience, Okazaki National Research Institutes, Okazaki, Aichi 444-8585, Japan
⁴CREST, Japan Science and Technology

(Requests for offprints should be addressed to T Iguchi, 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan)

Abstract

To evaluate mechanisms of cell proliferation in 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 Müllerian duct axis; these were proximal, middle and caudal, which differentiate into oviduct, uterus and upper vagina, respectively. In fetus 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 Müllerian duct. EGF levels were determined by immunohistochemistry. Müllerian 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 GD19.5 and was weak in the caudal epithelium, but substantially reduced throughout epithelia in all regions by GD21.5. Thus, decreased cell proliferation correlated with decreased EGF expression in the developing Müllerian duct. DES (100 mg/kg BW) was injected from GD15 to 19 and female fetuses were collected on GD19.5. DES increased Müllerian duct cell proliferation in the proximal epithelium and mesenchyme but decreased it in the caudal epithelium compared with oil controls. No proliferative DES effect was observed in any cell types in the middle region. Müllerian duct EGF immunoreactivity was suppressed by DES compared with oil. Competitive reverse-transcription polymerase chain reaction indicated DES also decreased mRNAs for EGF, ERb1 and ERb2, but not ERa and EGF-R. These results indicate EGF may be an important regulatory factor of Müllerian duct cell proliferation, and that DES may alter cell proliferation by disrupting normal EGF, ERb1 and ERb2 expression in the developing female rat reproductive tract.