[Studies on the physiological changes of blood coagulation factor XIII during pregnancy and their significance...

We measured the blood coagulability in pregnancy. Factor XIII, that showed unusual variations in these experiment, was investigated for its biological significance. The results are summarized as follows: 1) Blood coagulation factors XII, IX, VIII, VII and X, prothrombin and plasminogen showed a increasing tendency as the course of pregnancy. These was not very much change in factor V and plasmin activity during pregnancy. Factor XI showed a decreasing tendency. The further dramatic variation appeared in each coagulation factor at the onset of labor. 2) With regards to the factor XIII, XIII-S a carrier protein was inclined to increase from the value of 94.0 +/- 16.0% before pregnancy and reached the value of 109 + 16.3% at the last stage of pregnancy, while XIII-A an active site showed a decreasing tendency from 97.5 + 17.5% before pregnancy to 67.0 + 12.0%. 3) In placenta homogenate XIII-A was observed, but XIII-S absent. In retro-placental blood XIII-S was observed, but no XIII-A was seen. No significant difference between uterine venous blood and maternal peripheral blood was recognized. 4) The placental localization of XIII-A was investigated by the methods of fluorescent antibody technique and enzyme labeled antibody technique. XIII-A appeared in syncitiotrophoblast, but was not found in stroma, vessel wall and fetal side. In regards to decidua region its presence was not confirmed.