Preterm labor and bacterial intra-amniotic infection: arachidonic acid liberation by the action of phospholipase A2.

There is a strong association between preterm labor and infection, presumably through an increase in prostaglandin (PG) formation. The studies presented in this report were undertaken to evaluate whether bacterial products stimulate endogenous phospholipid hydrolysis and arachidonic acid liberation by the action of phospholipase A2, a rate-limiting step for PG synthesis. When human endometrial cells prelabelled with [3H]arachidonic acid to an isotopically steady state were exposed to a medium conditioned with Bacteroides fragilis, arachidonic acid liberation was stimulated, accompanied with lysophospholipid formation. Similar stimulatory effect on phospholipid degradation was also observed in the experiments with the bacterial extract. These results demonstrate that the organism produces phospholipase A2 acting on endogenous phospholipids and/or factor(s) activating phospholipase A2. Phospholipase A2 is suggested as a mechanism for the onset of labor associated with intra-amniotic infection and arachidonic acid liberation.