Assessment of placental functions using placenta-originating enzymes in maternal serum (author's transl)

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The purpose of the present investigation was to know whether the measurements of enzyme activities were of use in assessing the placental functions and of diagnostic value. A total of 2, 660 samples from the sera of 506 pregnant women and 42 samples from placental tissues were assayed for cystine aminopeptidose (CAP), leucine aminopeptidase (LAP) and heat stable alkaline phosphatase (HSAP). And the following results were obtained.(1) As regards enzyme concentrations in the placental tissue, CAP and LAP in a toxemic pregnancy showed lower values than those in a normal pregnancy. Nevertheless, in the case of a toxemic pregnancy, CAP and LAP in the maternal serum exhibited higher values than those in the placental tissue, and there were no correlations between the enzyme activities in the placental tissue and those in the maternal serum. As for HSAP, its values were low in both the placental tissue and the maternal serum. In the case of SFD, HSAP had a tendency to have a low value in both the maternal serum and the placental tissue.(2) In a normal pregnancy, there was a correlation between the concentration of the given enzyme in the maternal serum and the total quantity of the enzyme in the placental tissue (γ= 0.54 in CAP, γ =0.57 in LAP, r=0.60 in HSAP). On the other hand, in an abnormal pregnancy, there was a rise in the correlation cofficient for HSAP (γ =0.74) whereas the correlation cofficient for LAP was 0.44.(3) The activities of CAP, LAP and HSAP in serum increased as the gestational week advanced. Curves representing the variations in concentrations of these enzymes during a normal pregnancy consisted of two parts, i. e., the initial part where concentrations increased at a fixed rate and the late part where they increased at a continually decreasing rate.(4) The enzyme activity index (actual value-to-predictional value ratio) was derived. The index clearly showed the difference between the actual and the predicted values. Furthermore, a conversion table was made to simplify the calculation of the predictional value.(5) According to the activity index, one or more of these enzymes exhibited abnormal values in 76.46% of SFD (small for dates baby), 92.6% of toxemia of pregnancy and 50% of mild toxemia of pregnancy.