脑缺血预处理对大鼠海马CA1区一氧化氮合酶活性和一氧化氮含量的影响

Effect of cerebral ischemic preconditioning on NOS activity and NO content in the CA1 region of the hippocampus in rats

目的:观察脑缺血预处理(CIP)后大鼠海马一氧化氮合酶(NOS)活性和一氧化氮(NO)含量的变化,探讨NO在脑缺血耐受(BIT)诱导中的作用。方法:将140只凝闭双侧椎动脉的Wistar大鼠分为sham、CIP组、损伤性缺血组和CIP+损伤性缺血组。夹闭双侧颈总动脉致全脑缺血3min作为CIP,10min作为损伤性缺血,第4组中CIP与损伤性缺血之间间隔3d。所有动物均于末次脑缺血恢复再灌注后0h、2h、16h、24h、36h、72h和7d(每个时点n=5)取海马CA1区脑组织,分光光度法检测NOS活性,硝酸还原酶法检测NO2-/NO3-含量。结果:CIP组NOS活性和NO2-/NO3-含量于再灌注后16h开始升高,24h达高峰,接近sham组的1.5倍,36h降至基础水平,其升高的持续时间短于BIT诱导的时程(1-7d);损伤性缺血组NOS活性和NO2-/NO3-含量的变化趋势与CIP组类似,但其峰值(24h)超过sham组的2倍,显著大于CIP组(P<0.05);CIP+损伤性缺血组NOS活性和NO2-/NO3-含量亦有一定程度的升高,但其峰值(24h)明显低于损伤性缺血组(P<0.05)。结论:CIP引起NOS活性及NO2-/NO3-含量的适度增加,参与BIT的诱导;同时CIP阻止损伤性缺血后NO的过量生成所致的细胞毒性作用可能是其诱导BIT的另一途径。

AIM： To explore the role of NO in the induction of brain ischemic tolerance （BIT） by observing changes of NOS activity and NO2^-/NO3^- content following a transient cerebral ischemia. METHODS： The rat 4 - vessel occluding brain ischemic model was used. 140 male Wistar rats were divided into sham, cerebral ischemic preconditioning （CIP）, ischemic insult and CIP ＋ ischemic insult groups. An occlusion of the 4 vessels for 3 min was normally used as CIP, and a relative long one for 10 min was used as ischemic insult. When CIP was followed by ischemic insult, the interval between them was 3 d. The CA1 region of the hippocampns of rats was dissected out at 0 h, 2 h, 16 h, 24 h, 36 h, 72 h and 7 d after the last time of ischemia to assay its NOS activity and NO2^-/NO3^- content. RESULTS： The NOS activity and NO2^-/NO3^- content began to increase at 16 h, peaked at 24 h and decreased to basal level at 36 h of reperfnsion after CIP. The duration of the up - regulation of NOS activity and NO2 ^- / NO3^- content was much shorter than that of BIT, which usually takes place 1 - 7 d after CIP. The pattern of upregulation of the NOS activity and NO2^-/NO3^- content was similar to the CIP group, but the maximum （24 h） was much more than that in CIP group （ P 〈 0.05）. In the CIP ＋ ischemic insult group, the NOS activity and NO2 ^-/NO3 ^- content increased at 2 h of repeffusion, but the maximum （24 h） were much lower than that in ischemic insult group （ P 〈 0.05）. CONCLUSION： A moderate increase in NOS activity and NO production after CIP might participate in the induction of BIT by triggering a series of cellular signal transduction. In addition, inhibiting effect of CIP on over- production of NO caused by ischemic insult might be another way to induce BIT.