The mechanisms of preterm labour; the interaction between amnion cells and leukocytes in the metabolism of arachidonic acid.

Chorioamnionitis is frequently associated with preterm labour. We have used a cell culture model system to examine the effects of leukocytes upon the metabolism of endogenous arachidonic acid from within amnion cells. We have demonstrated that activated leukocytes release substances which increase the overall release and metabolism of endogenous arachidonic acid within amnion cells causing an increase in prostaglandin E2 production as well as a smaller increase in non-cyclo-oxygenase metabolism. When amnion cells and leukocytes are cultured together, in addition to prostaglandin E2 production by amnion cells, arachidonic acid released by the amnion cells appears to be metabolised by leucocytes to prostaglandin F2 alpha, prostacyclin and thromboxane A2. Prostaglandins E2 and F2 alpha are the principal cyclo-oxygenase products of this interaction. We postulate that chorioamnionitis stimulates preterm labour not only by causing an increase in prostaglandin E2 synthesis by amnion cells but by metabolism of amnion derived arachidonic acid to the powerfully oxytocic prostaglandin F2 alpha by leukocytes.