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Expression and activation of ERK and JNK in the hippocampus of rats exposed to global cerebral ischemia

Effects of the global cerebral ischemia on the ERK and JNK expression and activation signals in the hippocampus of rats exposed to global cerebral ischemia were studied. Animals were exposed to global cerebral ischemia (20 min duration) and after different reperfusion periods (5 and 10 min ; 1 ; 6 and 12 h after ischemia), ERK and JNK expression and activation signals were determined. Transient global cerebral ischemia was induced by the four-vessel occlusion method described by Pulsinelli and Buchan (1988). Total protein (35 μg) was loaded for each sample onto a 12% polyacrylamide gel. Membranes were probed with anti-ERK/JNK and anti-phospho ERK/JNX antibody (diluted 1:5000 in blocking buffer) overnight at 4 °C. A a-rabbit horseradish peroxidase-conjugated secondary antibody (diluted 1:4000 in 5% low fat milk in TBS+T) was utilized to allow detection of the appropriate bands using enhanced chemiluminescence reagent and film. Three animals in each experimental group were used to analyze the levels of proteins by Western blot. Results: The expression levels of ERK and JNK in the hippocampus remained constant during all reperfusion periods examined. The levels of phosphorylated ERK and JNK increased with time during the first 6h of reperfusion. After 6h, the amount of phosphorylated JNK had returned to control level. The levels of ERK appeared to return to peak levels after 12h of reperfusion in the second wave of kinase activation. Conclusions: Our results indicated that expression and activation of ERK and JNK were implicated in the early and the later periods of reperfusion injury in hippocampi of global cerebral ischemia exposed rat.

global cerebral ischemia; ERK; JNK; hippocampus; rats

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