Conversion of PGE 2 to PGF 2α by fetal sheep blood

Abstract

In an attempt to explain the differences in the concentration of primary prostaglandins in the circulation of adult and fetal sheep, we have examined the ability of whole blood from adult and fetal sheep to reduce PGE 2 to PGE 2α in vitro . PGF 2 was the principal radioactive product formed from 3H PGE 2 by both adult and fetal blood. The enzyme initial reaction velocity was significantly higher (P = 0.02) per ml of fetal than adult blood. The optimum enzyme pH (7.0 – 7.5) was similar for both adult and fetal blood. The Km of the enzyme in fetal and adult blood were 3.59 × 10 −7 M and 5.02 × 10 −7 M respectively (P > 0.05). There was no detectable metabolism of PGF 2α by either adult or fetal sheep blood. The results indicate that prostaglandin 9-ketoreductase is present in both adult and fetal sheep blood. Differences in the activity of this enzyme are unlikely to explain the higher concentrations of PGE reported in the plasma of fetal lambs.