Eicosanoids are thought to be important in the pathogenetic mechanism of ischemic brain damage. But little is known about lipoxygenase products and their roles in brain. In the present study, lipoxygenase metabolism in the brain and its relevancy to ischemic brain edema were studied using high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The rat middle cerebral artery (MCA) occlusion model was used because the time course of ischemic edema formation has been well known. The rat brain was fixed by in situ freezing 24 and 72 hours after MCA occlusion, and removed. Identification and quantitative analysis of hydroxyeicosatetraenoic acids (HETEs) in normal and ischemic brain homogenates was performed by HPLC and GC-MS. The rat brain was divided into the microvessel (MV) fraction and the rest. Then the same analysis was carried out in the both fractions obtained from the normal rat brain. Only 11-HETE was detected in the normal and ischemic brain. Quantitatively, normal brains contained 1288 +/- 66 (mean +/- SE) of 11-HETE ng/g wet weight, while the hemispheres rendered ischemic for 24 and 72 hours after MCA occlusion contained 1101 +/- 48, and 1663 +/- 147, respectively. The 11-HETE content was significantly increased 72 hours after MCA occlusion (p less than 0.05). The MV fraction of rat brain contained 11-HETE (653 ng/mg protein) ten times as much as the other fraction. The identification of 11-HETE in the rat brain is a new finding.(ABSTRACT TRUNCATED AT 250 WORDS)