Lipid metabolites including prostaglandins, leukotrienes, and platelet activating factor (PAF), as well as various monokines, are produced during parturition. Both fetal and maternal membranes axe implicated in this production. Understanding the metabolic pathways involved in eicosanoid production by these tissues is important in elucidating the steps involved in both normal and preterm initiation of parturition. This project aims to determine the mechanism of prostaglandin control in a well defined system, a macrophage-like cell line, and then to apply this knowledge to the more complex case of fetal and decidual membranes. The macrophage-like cell line is ideal as a model because the decidua exhibits several macrophage-like characteristics. Also, the correlation of bacterial infection and preterm labor suggests that a common mechanism may exist in the way these two cell types respond to stiinuli. Both responses seem to be intimately tied to the production of prostaglandins. The putative control step in the generation of eicosanoids is the release of arachidonic acid from the sn-2 position of membrane phospholipids by phospholipase A2. Our laboratory has succeeded in separating several phospholipases and solubilizing and purifying a membrane-associated phospholipase A2 from the transformed cell line P388D 1. This cell line has the usual characteristics of a macrophage, including the production of IL-1 and the major prostaglandins including PGE2, PGF2 alpha, and PGI2. Inhibitors of eicosanoid production in vivo will be identified and will then be evaluated for their ability to also inhibit the phospholipase(s) found in these cells. There should be a strong correlation between inhibition of eicosanoid production in vivo and the inhibition in vitro of the phospholipase actually involved in arachidonic acid release. Use of these methods should allow us to unequivocably identify the relevant phospholipase. Chemical inhibitors such as the anti-inflammatory compound manoalide and its analogs will be studied in this system as well as possible natural protein inhibitors of the lipocortin type and inhibiting monoclonal antibodies. Once the system is perfected with the P388D 1 cell line, we will be able to analyze human amnionic and decidual membranes in both resting and activated forms.