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(190) CHANGES AND REGULATION OF BLOOD VESSEL STABILITY IN RAT CORPUS LUTEUM DURING PREGNANCY. Sakata, Aki1, Taketani, Toshiaki1, Yamagata, Yoshiaki1, Sugino, Norihiro1, 1 Department Obstetrics and Gynecology, Yamaguchi,Ube, Japan ABSTRACT- Angiogenesis plays an important role in the development of the corpus luteum (CL), and blood vessel stability is an important factor for angiogenesis. Blood vessel stability is regulated by angiopoietin-1 (Ang-1) and Ang-2. Ang-1 contributes to blood vessel stabilization through its receptor Tie2. Ang-2 antagonizes the action of Ang-1. The present study was undertaken to investigate the change of blood vessel stability and its regulation in the rat CL during pregnancy. To evaluate blood vessel stability in the CL during pregnancy, we examined the vascular leakage (VL) on days 3, 7, 9, 12, 15 and 21 of pregnancy. Evans Blue (EB, 30 mg/kg) was injected via femoral vein and the ovaries were removed 30 min after injection. EB in the CL was extracted with formamide and the amount of EB was determined by absorption at 620 nm. In the CL after extraction, the number of blood vessel was counted in a grid area. Vascular index was estimated by multiplying the number of blood vessel by the CL weight. VL was determined by dividing the amount of EB by the vascular index. VL was highest on day 3, then decreased until day 15 and increased on day 21 again. Immunohistochemical study showed Ang-1 and Ang-2 expression in luteal cells. Ang-1 mRNA and protein levels were significantly higher on days 12 and 15 than those on days 3 and 21, whereas there was no significant change in Ang-2 expression during pregnancy. To study whether estrogen is involved in the change of VL and Ang expression between day 12 and day 15, rats undergoing hypophysectomy-hysterectomy (Hypox-Hect) on day 12 were daily treated with estradiol (E; 100 KEY WORDS: angiogenesis, vascular stability, corpus luteum, angiopoietin |
g) until day 15. VL was increased and Ang-1 expression was decreased by Hypox-Hect, and these effects were completely reversed by E treatment. In conclusion, the present study showed that blood vessel stability in the rat CL was parallel to the development of CL and regulated by estrogen through angiopoietins.