THE ROLE OF HSP70 IN ISCHEMIC TOLERANCE INDUCED BY ISCHEMIC PRECONDITIONING IN RATS

Objective To explore the role of heat shock protein 70(HSP70) in ischemic tolerance induced by ischemic preconditioning in rats.Methods Forty-eight healthy SD rats were divided randomly into six groups.The brains were obtained for the study as follows: group A,7 days after sham operation;group B,7 days after 3 min's cerebral ischemia;group C,2 days after 6 min's cerebral ischemia;group D,7 days after 6 min's cerebral ischemia;group E,3 min's ischemic preconditioning was followed 3 days later by 6 min's cerebral ischemia,the brains were then obtained 2 days after the last ischemia;group F,3 min's ischemic preconditioning was followed 3 days later by 6 min's cerebral ischemia and the brains were obtained 7 days after the last ischemia.The histological changes in CA1 subfield of hippocampus were examined with H.E staining,and the expression of HSP70 was detected by immunohistochemical analysis.Results Histological studies showed no significant neuron damage in the hippocampus CA1 subfield in groups A and B.There was severe neuron necrosis in group D,partial damages in groups C,E and F.The differences of neuron damage between group A and groups C,D;group D and group F,were statistically significant(F=19.6,q=4.766-12.447,P0.01).Immunohistochemical analysis showed that no HSP70 expression was found in groups A,C and D.In those preconditioning groups(E and F),HSP70 was expressed all over hippocampus CA1 subfield.There were significant differences in HSP70 expression between groups C and E,and between groups D and F(F=210.8,q=8.277-32.133,P0.01).Conclusion Ischemic preconditioning exhibited protection against neuronal death following subsequent fatal cerebral ischemia.HSP70 plays an important role in the ischemic tolerance induced by ischemic preconditioning.