Changes in the Levels of Eicosanoids and Isoprostane (8-iso-PGF2alpha) in the Newborn Rat Brain after Hypoxic-Ischemic Injury

ABSTRACT

PURPOSE: The changes in the levels of eicosanoids and isoprostane (8-iso-PGF2alpha) were investigated in brain tissue of 7 day-old rats after hypoxic-ischemic (HI) injury. METHODS: The 7 day-old newborn rats underwent right unilateral common carotid artery ligation followed by exposure to hypoxia with 8% oxygen for 150 minutes. There after, the pups were decapitated during reoxygenation 21% period of 0, 1, 6, 24, and 72 hours and their cerebral hemisheres were dissected through sagittal plane. Ipsilateral and contralateral cerebral hemesheres to common carotid artery ligation were used to determine the water content for estimation of severity of brain edema (n=5) and to measure the levels of eicosanoid and isoprostane (n=7). The levels of 6-keto-PGF1alpha, TXB2, and PGE2 were measured by RP-HPLC (reversed-phase high-performance liquid chromatography) and the levels of isoprostane (8-iso-PGF2alpha) were measured by enzyme immunoassay. The changes of eicosanoid and isoprostane levels during reoxygenation period were observed and comparisons between ipsilateral and contralateral hemispheres were done. RESULTS: The edema of ipsilateral cerebral hemesheres to common carotid artery ligation was more severe than that of contralateral cerebral hemisheres (P<0.05). The levels of 6-keto-PGF1alpha, TXB2, and PGE2 were found to increase during the early period of reoxygenation after HI insult, peak at 1 hour, and then decrease to the control levels at 72 hour (P<0.05). But, the levels of 8-iso-PGF2alpha did not significantly increase during the period of reoxygenation. The levels of 6-keto-PGF1alpha, TXB2, and PGE2 of ipsilateral hemispheres had a tendency to be higher than those of contralateral hemispheres during the initial 6 hour reoxygenation period, but the levels of 8-iso-PGF2alpha of ipsilateral hemispheres were significantly higher than those of contralateral hemispheres during the relatively later reoxygenation period (P<0.05). CONCLUSION: Reoxygenation after hypoxic-ischemic injury increased the levels of 6-keto-PGF1alpha, TXB2, and PGE2 in 7 day-old rat brain during the early period of reoxygenation, but the levels of isoprostane (8-iso-PGF2alpha) were not significantly increased during the reoxygenation period after HI injury.