Increased lipid peroxidation in vulnerable brain regions after transient forebrain ischemia in rats.

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Abstract
We examined cerebral lipid peroxidation, estimated by a thiobarbituric acid test, in rat brain regions after 30 minutes of severe forebrain ischemia and at recirculation periods of up to 72 hours. The lipid peroxide levels remained unaltered in all brain regions during ischemia and during the first hour of recirculation but were selectively increased between 8 and 72 hours of recirculation in the ischemia-sensitive regions of the hippocampus, striatum, and cortex. The most pronounced increases (30-37%) were seen at 48 hours of recirculation. In contrast, lipid peroxide levels were unchanged in infarcted brain regions 24 hours after intracarotid injection of microspheres, indicating that reoxygenation of the ischemic brain is a prerequisite for lipid peroxidation. We assessed the lipid peroxidation capacity of cerebral homogenates obtained from rats subjected to ischemia and recirculation by measuring the production of lipid peroxides after aerobic incubation. The homogenates from rats exposed to 30 minutes of ischemia or to 1 hour of recirculation were not more susceptible to peroxidation. However, the production of lipid peroxides was selectively increased in the hippocampus, striatum, and cortex at 8-48 hours of recirculation, suggesting a loss of efficacy of the antioxidant systems. These results, showing a delayed and long-lasting increase in lipid peroxidation that occurs in ischemia-sensitive brain regions and parallels the development of neuronal necrosis, support the hypothesis that free radical processes participate in postischemic neuronal damage.