LIPOPOLYSACCHARIDE-, LIPOSOME-ENCAPSULATED MTP-PE- AND DEXAMETHASONE- REGULATED PROSTAGLANDDV RELEASE IN RAT LIVER MACROPHAGES: ROLE OF CYTOSOLIC PHOSPHOLIPASE A_2 AND PROSTAGLANDIN H SYNTHASE-2

摘要

Rat liver macrophages (RLM), activated by a variety of agents, are known to release various eicosanoids including prostaglandin (PG)E_2 and PGD_2. The formation of prostanoids is strictly dependent on Ca~(2+) and is thought to be determined by the activation of a phospholipase (PL)A_2 and the expression of prostaglandin H synthase (PGHS)-2. It has been shown that RLM express an intracellular cPLA_2 which is strictly Ca~(2+)-dependent in the range from 10~(-7)-10~(-6) M and which shows a Ca~(2+)-dependent translocation to cellular membranes. cPLA_2 phosphorylation has been shown to be most likely catalysed by mitogen activated protein (MAP) kinase. Further evidence has been provided that in addition to regulation by cPLA_2, release of prostanoids in RLM is also dependent on the expression of PGHS-2.