凝血酶能刺激人的内皮肤细胞PGI_2的形成。但是以往对阻止PGI_2形成过多的抵销过程并没有描述过。在本研究中,我们证明Xa因子能抑制PGI_2合成,此合成是通过凝血酶或花生四烯酸诱导的,所需Xa的浓度表明,在血浆中仅是2％的X因子起激活作用。这种抑制作用被直接针对Va因子轻链的人类单克隆抗体所逆转。这就表明向下调节PGI_2的形成需要Va因子。融合的人内皮细 Thrombin can stimulate the formation of human inner skin cells PGI_2. However, the excessive elimination of PGI_2 in the past has not been described. In this study, we demonstrated that Factor Xa inhibits PGI2 synthesis induced by either thrombin or arachidonic acid and that the required concentration of Xa indicates that only 2% of Factor X in plasma is active. This inhibition is reversed by the human monoclonal antibody directed against the light chain of factor Va. This shows that the down-regulation of PGI_2 requires Va factor. Fusion of human endothelial thin