Different types of plasminogen activator inhibitors in plasma and platelets in pregnant women.

The content of tissue plasminogen activator inhibitor (t-PA-I), and of specific pregnancy plasma-PA-I reacting with antibodies to placental-PA-I, was measured in platelet-poor plasma (PPP), platelet-rich plasma (PRP), serum and platelet lysate, both from pregnant women and healthy non-pregnant (male or female) controls. Inhibitory activity was much higher in PPP from pregnant women than in PPP from controls, though it was comparable in platelet lysates both from pregnant women and from controls. The specific pregnancy Plasma-PA-I was present in high concentration in pregnancy PPP, but absent in PPP from the controls and also absent in platelet lysates from both pregnant women and controls. The results show that the specific pregnancy plasma-PA-I is not identical to either the PA-I in platelet lysate or to the PA-I in PPP from non-pregnant controls.