ISCHEMIC BRAIN EDEMA FOLLOWING OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY IN THE RAT .2. ALTERATION OF THE EICOSANOID SYNTHESIS PROFILE OF BRAIN MICROVESSELS

Using the rat middle cerebral artery occlusion model, alterations in the eicosanoid synthetic capacity of brain microvessels following ischemia were studied by radiochromatography. Brain microvessels of normal rats predominantly produced hydroxyacids with relatively small amounts of PG[prostaglandin]D2 and PGE2 from exogenous arachidonic acid. Confirmation that hydroxyacids and PG were products, respectively, of lipoxygenase(s) and cyclooxygenase was obtained by experiments using indomethacin and eicosatetraenoic acid. The eicosanoid synthetic capacity of the brain microvessel, especially of hydroxyacids, was significantly enhanced 24 and 72 h after the onset of ischemica. Because this is the phase of maximum edema in the present model, enhanced eicosanoid production in the brain microvessel may be involved in the mechanisms that underly ischemic brain edema.