Initiation of human parturition. XII. Biosynthesis and metabolism of prostaglandins in human fetal membranes and uterine decidua.

Prostaglandin synthetase activity was assayed in homogenates prepared from human fetal membranes and uterine decidua tissues with [14C] arachidonic acid used as substrate. In amnion, chorion laeve, and decidua vera tissues obtained after the spontaneous onset of labor and vaginal delivery the mean specific activities of prostaglandin synthetase were respectively 1.47, 0.53, and 0.39 nmoles x hr-1 x gm-1 tissue; in these same tissues obtained at elective cesarean section before the onset of labor the mean specific activities of prostaglandin synthetase were respectively 0.61, 0.33, and 0.28. The specific activity of prostaglandin synthetase of amnion (but not chorion laeve or decidua vera) was significantly greater in samples obtained after labor than in those obtained before labor (p less than 0.02). Prostaglandin synthesis in amnion, chorion laeve, and decidua vera was inhibited by acetylsalicylic acid and by indomethacin. Prostaglandin E2 was formed in amnion and chorion laeve, whereas prostaglandin E2 and prostaglandin F2 alpha were formed in decidua vera. The activity of NAD+ -dependent 15-hydroxyprostaglandin dehydrogenase was also assayed and the specific activities of this enzyme in chorion laeve and decidua vera tissues obtained before and after labor were high, whereas 15-hydroxyprostaglandin dehydrogenase activity in amnion was low.