Inhibition of fibrinolysis in pregnancy
Two immunologically distinct PAIs, PAI-1 and PAI-2, exist in the maternal circulation during pregnancy. SDS-PAGE with zymography showed pregnancy plasma contained 40kDa PAI-1, 75kDa α2-antiplasmin and two novel bands of PAI-2 at 130kDa and 75kDa. The size and intensity of the bands of PAI-1 and PAI-2 increased during pregnancy. Non-denaturing PAGE with zymography was developed for semiquantitative analysis of PAI-2. PAI-2 migrated as fast and slow bands on non-denaturing PAGE, which corresponded to 75kDa and 130kDa PAI-2 detected after SDS-PAGE. Fast PAI-2, the major form, was detected between nine weeks and six days postpartum. During pregnancy the bands of fast and slow PAI-2 increased in size and intensity to a maximum at 30-35 weeks. An ELISA, specific for PAI-2 antigen, was developed which used a rabbit antibody raised against human placental PAI-2. With a detection limit of 1.8 ng/ml, this ELISA was used to quantify PAI-2 in plasma and body fluids. Plasma PAI-1 and PAI-2 increased to maximum concentrations of 112.5 ± 28.9 ng/ml and 197.3 ± 56.9 ng/ml respectively during the third trimester and decreased slightly before delivery. After delivery PAI-1 decreased rapidly, while PAI-2 persisted longer in the maternal circulation. The postpartum half-lives of PAI-1 and PAI-2 were determined as 30 minutes and 24 hours respectively. Plasma from pre-eclamptic subjects showed elevated PAI-1 and decreased PAI-2. Plasma from pregnant subjects with DIC also showed increased PAI-1 and decreased PAI-2. PAI-2 was not detected in plasma during molar pregnancy. Amniotic fluid contained PAI-1 and fast PAI-2. Amniotic fluid PAI-1 doubled between 16 weeks and term, while PAI-2 decreased slightly. Term amniotic fluid PAI-1 was 8-fold higher than PAI-2. PAI-2 was also detected in ovarian cyst fluid, plasma from subjects with pancreatitis, septicaemia and leukaemia showing that PAI-2 is not a pregnancy-specific protein.