The role of placental urokinase inhibitor in toxemia of pregnancy.

The fibrinolysis of the uterus can be reversed during the course of pregnancy. The chief cause of this physiologic change is an increase of urokinase (UK) inhibitor in the placenta. The UK inhibitor also has a pathologic aspect that can influence the course of pregnancy. We have proven that the hypofibrinolysis of toxemic pregnant urine results from increased UK inhibitor. Furthermore, we have shown the existence of UK inhibitor in toxemic pregnant serum and the glomerulus. On the basis of these facts we propose that UK inhibitor leaks into the maternal blood stream from the placenta and inhibits the fibrinolytic activity of UK, forming microthrombuses in the glomerulus. Excess UK inhibitor in the placenta also suppresses the fibrinolytic activity of placental plasminogen activator (PPA). Thus microthrombuses are apt to be formed in both the placenta and glomerulus. Such pathologic inhibition of fibrinolysis strongly influences the course of toxemia.