Exposure to absolute oxygen pressure of 3 and 5 bar revealed hemispheric and interhemispheric differences in lipid peroxidation and the content of phospholipids in rat brain. Key Words: synaptosomes; phospholipids; hyperbaric oxygen," brain asymmetryGeneration of reactive oxygen species (0-2, HO , and H202) inducing peroxidation of lipids, proteins, and nucleic acids and, therefore, leading to membrane destruction and nervous cell death, accounts for neurotoxic effects of hyperbaric oxygen (HBO2) [3,8]. Changes in lipid peroxidation (LPO) and lipid composition of cell membranes in symmetrical brain structures induced by stress, ischemia, and other factors are different in rats demonstrating various patterns of behavior [4,5]. Therefore, HBO 2 can cause different cytostructural damages to right and left brain structures.Here we studied interhemispheric asymmetry in LPO and content and composition of phospholipids (PL) in synaptosomal fraction of brain hemispheres of rats exposed to HBO 2. MATERIALS AND METHODSExperiments were performed on 26 outbred male rats weighing 150-200 g. The animals were divided into 4 groups. Group 1 rats (1l=8) served as the control (open decompression chamber) and were exposed to air at atmospheric pressure. Animals of groups 2 (n=6) and 3 (n=6) were exposed to absolute oxygen pressure of 3 and 5 bar, respectively. Group 4 rats (n=6) were intravenously injected with superoxide dismutase (Cu/ Compression was performed in a pressure chamber (400 liters) at a rate of 1 bar/min for 30 min. After decompression, the animals were decapitated, and the right and left hemispheres were removed. Synaptosomes were isolated as described elsewhere [10], and protein concentration was determined [12]. Total PL were extracted [9] and fractionated to phosphatidylserine, phosphatidylinositol, sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine by twodimensional microthin layer chromatography using chloroform:methanol:28% ammonia (65:35:5) and chloroform:methanol:acetone:acetic acid:I-I20 (50:10: 20:10:5) systems. KSK silica gel (5-H fraction) containing 10% gypsum served as the sorbent. Quantitative analysis of PL was performed as described previously [13]. The intensity of LPO was evaluated by the content of MDA [1]. The results were analyzed using Student's t test and STATGRAPHICS 3.0 software.Laboratory

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