Comparative study of proteinase inhibitors in human amniotic fluid and maternal serum.

Serum and amniotic fluid samples from five pregnant women were analyzed for different proteinase inhibitors by ion-exchange chromatography on DEAE-cellulose. Alpha-2 macroglobulin was found to be absent in amniotic fluid. Even though alpha-1 antichymotrypsin was identified in amniotic fluid, its concentration gradient between serum and amniotic fluid (20--60) was much higher than that of alpha-1 antitrypsin (8--20). Two forms of alpha-1 antitrypsin were identified in both the fluids. In pregnancy, the ratio of the two forms was altered in favour of the less anionic form compared to normal sera. The contribution of the heat stable proteinase inhibitor for total antitryptic activity in amniotic fluid was more than in serum. The observation that urine samples from immature infants had higher heat stable inhibitory activity than urine samples from normal infants suggests that the heat stable inhibitor in amniotic fluid may arise from fetal kidney.