Initiation of human parturition. IV. Demonstration of phospholipase A2 in the lysosomes of human fetal membranes.

In this study we sought to define the subcellular localization of phospholipase A2 in human fetal membranes. Others have postulated a role for decidual lysosomes in the initiation of human parturition. We hypothesized that if phospholipase A2 were localized within lysosomes of fetal membranes the accelerated expression of the activity of this enzyme could be prevented until such time as the metabolic events of parturition begin. At parturition a perturbation of the lysosomal membrane within the chorio-amnion could result in an increased release of free arachidonic acid through an accelerated activity of phospholipase A2. The results of this study suggest that at least a portion of phospholipase A2 in the chorion laeve and amnion is localized in the lysosomal fraction.