Summary
Plasminogen activator inhibitor activity (PAI), PAI-1 and PAI-2 antigen, and other
fibrinolytic parameters were evaluated in amniotic fluid during normal pregnancy and
compared with that obtained in plasma of pregnant women. The results indicate the
presence of both PAI-1 and PAI-2 in amniotic fluid during normal pregnancy. In amniotic
fluid, PAI-1 antigen levels increased from 194 ± 109 ng/ml (first trimester) to 640
± 396 ng/ml (third trimester) and PAI-2 antigen levels increased from 72 ± 57 ng/ml
to 173 ± 97 ng/ml. In contrast, a decrease in tissue-type plasminogen activator (t-PA)
antigen level was observed during pregnancy. The PAI-1 levels in amniotic fluid were
significantly higher than the PAI-1 levels in plasma of women at a similar gestational
age. However, PAI activity, measured using single chain t-PA, was lower in amniotic
fluid than in plasma of normal pregnant women. The PAI activity/PAI-1 antigen ratio
in amniotic fluid after activation by a denaturing agent increased from 0.003 ± 0.004
to 0.059 ± 0.018. These results indicate that high levels of PAI-1 are present in
amniotic fluid and suggest that this PAI-1 is present in a latent form that can be
reactivated, at least partially, by a denaturing agent.
