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(256) EXPRESSION OF IGFBP-RP1/MAC25 AND ITS BIOLOGICAL ACTIVITIES ON RAT UTERINE CELLS DURING THE PERI-IMPLANTATION PERIOD. Tamura, Kazuhiro1, Kutsukake, Masahiko1, Hara, Takahiko2, Kogo, Hiroshi1, 1 Department of Endocrine Pharmacology, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo, Japan2 The Tokyo Metropolitan Institute of Medical Science, Honkomagome, Tokyo, Japan ABSTRACT- Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1)/mac25 is expressed highly in rat uterus around the day of implantation. In the present study, we determined the localization of IGFBP-rP1 mRNA in peri-implantation uterus in rats, and the effects of recombinant IGFBP-rP1 on the proliferation and prostacyclin (PGI2)-producing ability of cultured endometrial cells prepared from early pregnant uterus. We found that IGFBP-rP1 mRNA was highly present in endometrial stromal cells close to the smooth muscle of inter-implantation sites around the time of implantation. However, no IGFBP-rP1 mRNA signal was observed in the decidual zones surrounding the embryo in contrast to the intense signal in the endometrium of non-implantation sites (inter-implantation sites) just after implantation. Uterine IGFBP-rP1 expression was also increased as implantation was induced in the delayed implanting pregnant model, but the mRNA level was decreased as decidual tissues were formed in the decidualization model. Recombinant IGFBP-rP1 (100 ng/ml) inhibited the proliferation in endometrial stromal cells remaining in the G1 phase of the cell cycle in vitro. Furthermore, IGFBP-rP1 significantly stimulated the PGI2 synthesis and mRNA expression of cyclooxygenase in myometrial cell preparation, which are essential for the successful implantation in vivo. These data suggest that IGFBP-rP1 is an implantation-associated protein and modulates the proliferation and PGI2 production of rat uterine cells during the peri-implantation period. KEY WORDS: implantation, IGFBP-rP1, prostacyclin |
