Evaluation of lipid peroxidation, cathepsin L and acid phosphatase activities in experimental brain ischemia-reperfusion

This investigation was conducted in rat brain tissues to elucidate the free radical induced cellular and subcellular membrane injuries in two differen t depth of global ischemia. Global moderate (penumbral) ischemia was perfor med on rat brains by bilateral vertebral arteries cauterization and tempora ry occlusion of the bilateral carotid arteries. Global severe ischemia was produced by a neck tourniquet in addition to four vessel occlusion. Somatos ensory evoked potentials (SSEPs) were used as a feed back parameter to moni tor electrophysiologically the ischemia. Al the end of ischemic insult (0 m in reperfusion) or various reperfusion periods (20, 60 and 240 min), all ra ts were decapitated and brains were frozen in liquid nitrogen. The brain ti ssues were prepared for the determination of cathepsin L (CL) and acid phos phatase (AP) activities in the supernatant (cytosolic) fraction (SF) and th e fraction enriched with lysosomes (FEL). Further the level of thiobarbitur ic acid reactive substances (TEARS) of lipid peroxidation was assessed by t he spectrophotometric methods. Severe ischemia-reperfusion was accompanied by a significant increase in TEARS levels and the SF/FEL ratio for CL and A P activities compared to the sham operated group and the concurrent reperfu sion groups of moderate ischemia (p < 0.05). There were no significant diff erences between the sham operated and moderate ischemia-reperfusion groups for the same parameters. Our data clearly demonstrate that; in rat brain al though severe ischemia-reperfusion causes lipid peroxidation in cellular me mbranes and redistribution of lysosomal enzymes from lysosomes to cytoplasm due to lysosomal membrane injury, there are no changes in lysosomal membra ne stability in moderate ischemia-reperfusion. (C) 1999 Elsevier Science B. V. All rights reserved.