[A study on the activity of the PGI2 producing enzyme system derived from maternal and fetal vessels of toxemia of pregnancies].

We investigated the conversion rate from arachidonic acid (A.A.) to PGI2 and the activity of PGI2 producing enzyme system in endothelial cells of umbilical veins (U.V.) and maternal omental veins (O.V.) in normal pregnancy (NOR) and toxemia of pregnancy (TOX). The conversion rate from A.A. to PGI2 for U.V. and O.V. in NOR was higher than that in TOX. There was a significant difference between NOR and TOX with the conversion rate for U.V. at a concentration of 172.4 nM/ml A.A. The apparent Vmax value for PGI2 producing enzyme system (nM/mg) in U.V. in NOR (n = 7) was 0.88 +/- 0.21 (mean +/- S.E.) and that for TOX (n = 3) was 1.63 +/- 0.18. The apparent Km value for the enzyme system (microM) in U.V. in NOR (n = 7) was 0.75 +/- 0.25, and that for TOX (n = 3) was 3.26 +/- 0.78. Significant differences (p less than 0.05) between NOR and TOX were observed with Vmax and Km values. The apparent Vmax value for the enzyme system in O.V. in NOR (n = 3) was 0.32 +/- 0.13, and that for TOX (n = 3) was 2.12 +/- 0.38. The apparent Km value for the enzyme system in O.V. of NOR (n = 3) was 0.26 +/- 0.06, and that for TOX (n = 3) was 0.97 +/- 0.09. There was a significant difference between (p less than 0.05) the Vmax and Km values for NOR and TOX. The present study showed that U.V. (fetal vessel) and O.V. (maternal vessel) in TOX had a lower activity PGI2 producing enzyme system than those in NOR due mainly to an imbalance between the substrate supply and cyclooxygenase activity.