缺血后处理对大鼠脑缺血再灌注损伤的影响

Influence of ischemic postconditioning on cerebral ischemia-reperfusion injury in rats

目的探讨缺血后处理对大鼠局灶性脑缺血再灌注损伤的影响。方法 80只SD大鼠随机分为假手术组、缺血再灌注组、缺血后处理组和延迟缺血后处理组各20只,缺血再灌注组、缺血后处理组和延迟缺血后处理组采用改良Zea-Longa法制备大脑中动脉缺血再灌注模型,缺血再灌注组不作处理,缺血后处理组实施30s缺血+30s再灌注操作3个循环,延迟缺血后处理组再灌注15min后实施30s缺血+30s再灌注操作3个循环;假手术组仅结扎颈外动脉,不插入线栓。恢复灌注24h处死大鼠,取脑组织制作切片,应用图像处理软件计算脑梗死灶体积;提取右侧大脑半球线粒体,采用TBA法检测丙二醛含量,采用分光光度计法检测Na^+-K^+三磷酸腺苷酶(adenosine triphosphatase,ATPase)、Ca^(2+) ATPase和Mg^(2+) ATPase活性。结果假手术组未发现梗死灶,缺血再灌注组皮层及海马区见白色梗死灶,缺血后处理组皮层见苍白色梗死区,延迟缺血后处理组左侧皮层及海马区见苍白色梗死灶;缺血后处理组脑梗死灶体积[(30.81±3.63)%]较延迟缺血后处理组[(51.01±3.33)%]和缺血再灌注组[(54.25±3.69)%]小(P<0.05),延迟缺血后处理组脑梗死灶体积与缺血再灌注组比较差异无统计学意义(P>0.05);线粒体丙二醛水平在缺血再灌注组[(1.56±0.08)μm/g]、延迟缺血后处理组[(1.47±0.10)μm/g]和缺血后处理组[(0.87±0.04)μm/g]均高于假手术组[(0.40±0.06)μm/g],缺血再灌注组和延迟缺血后处理组高于缺血后处理组(P<0.05),缺血再灌注组与延迟缺血后处理组比较差异无统计学意义(P>0.05);Na^+-K^+ ATPase、Ca^(2+) ATPase和Mg^(2+) ATPase活性在缺血再灌注组(2.88±0.18、3.45±0.34、0.96±0.23)、延迟缺血后处理组(2.88±0.30、3.59±0.36、1.07±0.31)和缺血后处理组(4.93±0.17、4.91±0.40、2.59±0.26)均低于假手术组(6.12±0.71、6.75±0.23、3.79±0.33),缺血再灌注组和延迟缺血后处理组低于缺血后处理组(P<0.05),缺血再灌注组与延迟缺血后处理组比较差异无统计学意义(P>0.05)。结论缺血后处理可减轻局灶性脑缺血大鼠再灌注损伤,其机制可能与降低线粒体丙二醛表达、增加ATPase活性有关。

Objective To investigate the influence of ischemic postconditioning on focal cerebral ischemia-reperfusion injury in rats.Methods Eighty SD rats were randomly divided into sham operation group,ischemia-reperfusion group,ischemic postconditioning group and delayed ischemic postconditioning group,with 20 rats in each group.The models of middle cerebral artery ischemia-reperfusion were established by modified Zea-Longa method in ischemia-reperfusion group,ischemic postconditioning group and delayed ischemic postconditioning group.Ischemia-reperfusion group received no treatment.Ischemic postconditioning group was treated with 3 cycles of 30 s ischemia+30 s reperfusion before pulling out the bolt.Delayed ischemic postconditioning group was treated with 3 cycles of 30 s ischemia+30 s reperfusion after 15 min reperfusion.The rats in sham operation group were ligated the external carotid artery,without inserting the coil.After restoring perfusion for 24 h,the rats were sacrificed.The brain tissue was obtained to make a slice.The volume of cerebral infarction was calculated by image processing software.The right hemisphere mitochondria were extracted.The content of malondialdehyde was detected by TBA method.The activities of mitochondrial Na^+-K^+ adenosine triphosphatase(ATPase),Ca^(2+) ATPase and Mg^(2+) ATPase were detected by spectrophotometry.Results The brain tissue in sham operation group had no infarction.The cortex and the hippocampus in ischemia-reperfusion group were found white infarct focus.The cortex in ischemic postconditioning group had pale infarction.The left cortex and hippocampus in delayed ischemic postconditioning group had pale infarction.The cerebral infarction volume in ischemic postconditioning group((30.81±3.63)%)was significantly smaller than that in ischemia-reperfusion group((54.25±3.69)%)and delayed ischemic postconditioning group((51.01±3.33)%)(P<0.05),and there was no significant difference between delayed ischemic postconditioning group and ischemia-reperfusion group(P>0.05).The expression of mitochondrial malondialdehyde was significantly higher in ischemia-reperfusion group((1.56±0.08)μm/g),delayed ischemic postconditioning group((1.47±0.10)μm/g)and ischemic postconditioning group((0.87±0.04)μm/g)than that in sham operation group((0.40±0.06)μm/g)(P<0.05),and higher in ischemia-reperfusion group and delayed ischemic postconditioning group than that in ischemic postconditioning group(P<0.05),and there was no significant difference between ischemia-reperfusion group and delayed ischemic postconditioning group(P>0.05).The activities of mitochondrial Na^+-K^+ ATPase,Ca^(2+) ATPase and Mg^(2+) ATPase were significantly lower in ischemia-reperfusion group(2.88±0.18,3.45±0.34,0.96±0.23),delayed postconditioning group(2.88±0.30,3.59±0.36,1.07±0.31)and ischemic postconditioning group(4.93±0.17,4.91±0.40,2.59±0.26)than those in sham operation group(6.12±0.71,6.75±0.23,3.79±0.33)(P<0.05),and lower in ischemia-reperfusion group and delayed ischemic postconditioning group than those in ischemic postconditioning group(P<0.05),and there were no significant differences between ischemia-reperfusion group and delayed ischemic postconditioning group(P>0.05).Conclusion Ischemic postconditioning could relieve focal ischemia-reperfusion injury,and its mechanism may be correlated with the decrease of malondialdehyde expression and the increase of ATPase activity.