Lipopolysaccharide-, Liposome-Encapsulated MTP-PE- and Dexamethasone- Regulated Prostaglandin Release in Rat Liver Macrophages: Role of Cytosolic Phospholipase A2 and Prostaglandin H Synthase-2

Rat liver macrophages (RLM), activated by a variety of agents, are known to release various eicosanoids including prostaglandin (PG)E2 and PGD2 1. The formation of prostanoids is strictly dependent on Ca2+ and is thought to be determined by the activation of a phospholipase (PL)A2 2 and the expression of prostaglandin H synthase (PGHS)-2. It has been shown that RLM express an intracellular cPLA2 which is strictly Ca2+-dependent in the range from 10-7-10-6 M and which shows a Ca2+-dependent translocation to cellular membranes3,4. cPLA2 phosphorylation has been shown to be most likely catalysed by mitogen activated protein (MAP) kinase4. Further evidence has been provided that in addition to regulation by cPLA2, release of prostanoids in RLM is also dependent on the expression of PGHS-25.