Iron‐dependent peroxidation of rat brain: A regional study

Abstract

Iron has been shown to initiate a variety of free radical reactions in biological systems. The present study examined the in vitro susceptibility of homogenates prepared from different regions of rat brain to iron-induced peroxidation. Among the regions studied, basal thiobarbituric acid-reactive product (TBAR) formation is highest in the cerebellum and amygdala, intermediate in the cortex, hippocampus, and neostratium, and lowest in the hypothalamus, midbrain, and brainstem. In the presence of 200 microM FeCl3, there is a 20-25-fold increase in the net TBAR formation in all regions, with TBAR formation in the cerebellum and amygdala being significantly higher than in the midbrain and brainstem. Time-course and dose-response studies of iron-induced peroxidation showed that the cerebellum and amygdala are the most susceptible regions with respect to concentration of iron and duration of the incubation time, whereas the midbrain and brainstem are the least affected areas. Following low-speed (1,000 g) centrifugation of brain part homogenates, TBAR formation in the supernatant fractions is quite uniform across regions, while the pellet fractions give the same regional variations as the whole homogenates. TBAR formation in both fractions is increased 20-30-fold in the presence of 200 microM iron. Brain tissue TBAR formation induced by 200 microM iron is inhibited by the iron chelator desferrioxamine (IC50 = 600 microM), by Tris buffer pH = 8.0 (2.5 mM Tris gives 50% inhibition by trapping hydroxyl radicals), and by high concentrations of the cyclooxygenase inhibitor indomethacin (IC50 = 1.2 mM).

Lipid peroxidation measurement by thiobarbituric acid assay in rat cerebellar slices

“…It is likely that these results mainly represent the artifactual basal values of TBARS generated during the assay previously reported by several researchers (Gutteridge and Halliwell, 1990;Götz et al, 1993;Li and Chow, 1994). However, the concentrations of these basal values were significantly lower than those obtained in a previous study in supernatant cerebellum fractions (Subbarao and Richardson, 1990). The reason for such a discrepancy appears to be methodological.…”

“…Tissue homogenates were prepared on ice using a teflon pestle (10-12 strokes) and centrifuged at 3000 × g for 15 min. The supernatant that contained microsomes, mitochondria and synaptosomes (Subbarao and Richardson, 1990) was retrieved. From this supernatant, 20 l was taken to determine the amount of proteins using Lowry's assay (1951).…”

Pleurotus ostreatus, an edible mushroom, enhances glucose 6-phosphate dehydrogenase, ascorbate peroxidase and reduces xanthine dehydrogenase in major organs of aged rats

“…Remarkably, in the present study, a markedly reduced numbers of Apx isozyme found in the brain tissues of aged untreated rats suggests that the brain tissue may be particularly susceptible to oxidative stress. A possible reason for this could be that since the brain is rich in non-heme iron, it could be catalytically involved in the production of oxygen free-radicals (Subbarao & Richardson, 1990). Another possible explanation is that the presence of unsaturated fatty acids in high concentrations makes the brain tissue good substrates for the occurrence of peroxidation reactions (Ogawa, 1994).…”

Recovery of Motor Deficit, Cerebellar Serotonin and Lipid Peroxidation Levels in the Cortex of Injured Rats

“…The effect of iron accumulation is mediated by the formation of reactive species, including hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (•OH) [15,16]. Both •OH and the products of •OH can react with polyunsaturated fatty acids in cell membranes, increase rates of peroxidation in the brain and contribute to neuronal damage [10,16,17].…”

“…An injection of iron in the brain of animal models is associated with oxidative injury, neurodegeneration and neuron death [9][10][11][12][13][14]. The effect of iron accumulation is mediated by the formation of reactive species, including hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (•OH) [15,16].…”