Abstract: Objective To investigate expression of osteopontin (OPN) in the mouse oviduct during the estrous cycle and early pregnancy. Methods A total of 70 female and 15 male mice of Kunming white strains were used in this study. Immunohistochemistry and image analysis were employed to detect and analyze the localization and expression of OPN in the mouse oviduct during the estrous cycle, pregnant and pseudopregnant from day 1 to 5, respectively. Results Throughout the estrous cycle, the OPN immunostaining of mouse oviduct epithelium was positive. The average absorbance (AEM>A/EM>) of OPN in oviduct epithelium was the highest in the estrus stage, and the lowest in the diestrus stage. The OPN immunostaining was positive throughout day 1 to 5 of pregnancy and pseudopregnancy. The expression of OPN reached peak on day 4 of pregnancy. There were significant differences in the same day between the pregnancy and the pseudopregnancy in the AEM>A/EM> value of OPN druing day 3 to 5 (EM>P /EM>< 0.05,EM> P/EM> < 0.01, EM>P/EM> < 0.05). Conclusion The expresses of OPN in the mouse oviduct epithelium may be regulated by estrogen during the estrous cycle, which is regulated by estrogen and preimplantation embryos during early pregnancy.

Key words: Oviduct, Osteopontin, Estrous cycle, Pregnancy, Immunohistochemistry, Mouse 