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.⁵ 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.