Study on the Source of Increased Plasminogen Activators (tPA, uPA) and their inhibitors (PAI-1, PAI-2) in Pregnancy Plasma

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We measured the plasma levels of plasminogen activators (tPA, uPA) and their inhibitors (PAI-1, PAI-2) at various intervals during pregnancy, delivery and puerperium. Their antigens were measured by Biopool Tint Elize Kits. In the pregnancy plasma of the third trimester, the levels of the activators were about 2 times and those of their inhibitors were about 10 times higher than those in non-pregnancy plasma.To clarify whether the uterus and/or placenta are involved in the increased levels of plasma PA and their inhibitors, their levels were measured in the retroplacental blood (RPB) and the uterine venous blood (UVB). The level of tPA in the RPB was the same as that in the peripheral venous blood (PVB) but the levels of uPA, PAI-1 and PAI-2 in the RPB was about 2.5 times higher than those in the PVB. During the ante-partum period, only the level of uPA in the UVB was higher than that in the PVB, while there was no significant difference between the levels of tPA, PAI-1 and PAI-2 in the PVB and UVB. The level of tPA in the UVB rose after separation of placenta. In contrast, the level of uPA declined immediately after the separation. There was no significant difference between the levels of PAI-1 and PAI-2 in the UVB before and after removal of the placenta.The release of tPA from endotherial cell was enhanced in vitro by addition of the pregnancy plasmas obtained at the time of delivery.These results suggest that placenta, uterus and entire vascular system are involved in the increase of tPA and uPA during pregnancy but that the major source of their inhibitors in the pregnancy plasma are unknown.