Specific plasminogen activator inhibitor of placental type PAI 2 occurring in amniotic fluid and cord blood.

Plasminogen activator inhibitor of placental type (PAI 2) occurs in a high molecular weight form (HMW) of 60 kd and a low molecular weight form (LMW) of 48 kd. Amniotic fluid and umbilical cord and maternal term plasma were examined for presence of PAI 2 using an enzyme-linked immunosorbent assay sandwich technique, purification on an affinity column (monoclonal antibodies coupled to Sepharose 4B), and immunoblotting. The median values of the concentrations of PAI 2 were 89, 13, and 75 micrograms/L, respectively. The HMW and LMW forms were found at about the same concentrations in amniotic fluid, but the LMW form predominated in cord blood, and the HMW form in maternal blood. The physiologic function of PAI 2 in the child is probably to prevent bleeding during the hazards of parturition.