Inflammatory response to polyacryl starch microparticles, role of arachidonic acid metabolites

Abstract The effect of polyacryl starch microparticles on arachidonic acid metabolism in macrophage cultures and in mice was studied. When macrophages were incubated with the microparticles, significant amounts of arachidonic acid metabolites were released. Two of the major metabolites were identified and found to be prostaglandin E 2 and leukotriene C 4 . Intravenous administration in mice of slowly degradable polyacryl starch microparticles, having a mean diameter of 1 μm, resulted in hepatomegaly and occasionally, inflammatory granulomas in the liver. Rapidly degradable microparticles did not give the same response. When the mice were treated with inhibitors of arachidonic acid metabolism, i.e. indomethacin or timegadine, the microparticle-induced hepatomegaly was partly inhibited. The microparticle-mediated effects were compared with those obtained with a well-characterized macrophageactivating/inflammatory agent, 1,3-β-glucan particles.