Oxidative stress following traumatic brain injury in rats: Quantitation ofbiomarkers and detection of free radical intermediates

Oxidative stress may contribute to many pathophysiologic changes that occur after traumatic brain injury. In the current study, contemporary methods o f detecting oxidative stress were used in a rodent model of traumatic brain injury. The level of the stable product derived from peroxidation of arach idonyl residues in phospholipids, 8-epi-prostaglandin F-2 alpha, was increa sed at 6 and 24 h after traumatic brain injury. Furthermore, relative amoun ts of fluorescent end products of lipid peroxidation in brain extracts were increased at 6 and 24 h after trauma compared with sham-operated controls. The total antioxidant reserves of brain homogenates and water-soluble anti oxidant reserves as well as tissue concentrations of ascorbate, GSH, and pr otein sulfhydryls were reduced after traumatic brain injury. A selective in hibitor of cyclooxygenase-2, SC 58125, prevented depletion of ascorbate and thiols, the two major water-soluble antioxidants in traumatized brain. Ele ctron paramagnetic resonance (EPR) spectroscopy of rat cortex homogenates f ailed to detect any radical adducts with a spin trap, 5,5-dimethyl-1-pyrrol ine N-oxide, but did detect ascorbate radical signals. The ascorbate radica l EPR signals increased in brain homogenates derived from traumatized brain samples compared with sham-operated controls. These results along with det ailed model experiments in vitro indicate that ascorbate is a major antioxi dant in brain and that the EPR assay of ascorbate radicals may be used to m onitor production of free radicals in brain tissue after traumatic brain in jury.