Mobilization of arachidonic acid from specific glycerophospholipids of human fetal membranes during early labor.

Arachidonic acid is mobilized from the fetal membranes (amnion and chorion laeve) during human parturition. To define the lipid species that serve as the source of arachidonic acid, we determined the lipid composition of fetal membranes obtained before and during early labor. The arachidonic acid content of diacyl phosphatidylethanolamine decreased by 41% in amnion and 20% in chorion laeve during early labor. The arachidonic acid content of phosphatidylinositol decreased by 35% in amnion and 16% in chorion laeve. No statistically significant changes were found in the arachidonic acid content of the other lipid fractions of either amnion or chorion laeve. Thus, during early labor, there is a net release of arachidonic acid specifically from diacyl phosphatidylethanolamine and phosphatidylinositol of amnion and chorion laeve. The specific decrease in the arachidonic acid content of the diacyl phosphatidylethanolamine and phosphatidylinositol of human fetal membranes during early labor, as found in the present investigation, can be accounted for by enzymatic activities that are relatively specific for the release of arachidonic acid from these two glycerophospholipids.