Significance of the plasminogen activator inhibitor of placental type (PAI-2) in pregnancy

Marked changes in the hemostasis system, especially increases in PAI-2, are observed during pregnancy and at delivery, This inhibitor is produced by p lacental trophoblasts and by macrophages, PAI-2 occurs in two forms, a LMW and a HMW form. LMW PAI-2 is intracellular, HMW PAI-2 is secreted, PAI-2 in hibits both u-PA and two-chain t-PA. PAI-2 seems to be involved in the processes of invasion and remodeling of f etal and uterine tissues. It may protect against premature placental separa tion and secure hemostasis at parturition, Excess levels of PAI-2 in amniot ic fluid may protect membranes from premature rupture. An imbalance between fibrinolytic activators and inhibitors may also be related to intracranial hemorrhage in premature infants, During preeclampsia t-PA and PAI-1 levels are markedly increased in plasma, and in cases of intrauterine growth retardation, u-PA and PAI-2 levels are decreased. While elevated PAI-1 concentrations might be helpful markers of severity of preeclampsia, decreased PAI-2 levels seem to indicate decrease d placental function and intrauterine growth retardation.