心肌缺血时NO代谢的动态变化

目的:探讨心肌缺血过程中一氧化氮(NO)代谢的动态变化。方法:采用小鼠在体心肌缺血模型和大鼠离体心脏灌流模型,分别观察不同程度和时间缺血对心肌NO浓度的影响,并进一步观察缺血对心肌一氧化氮合酶(NOS)和NOS基因表达的影响。结果:在一定范围内,随着垂体后叶素(Pit)剂量的增加和Pit加入后时间的延长,心肌NO代谢产物浓度逐渐下降。在体实验中,Pit剂量为30U/kg及Pit注入后30min,心肌NO代谢产物浓度显著低于对照组(P<0.01);离体实验中,Pit剂量为200U/L和Pit加入后15min,心肌NO代谢产物浓度亦显著低于对照组(P<0.01)。同时,缺血组心房肌和心室肌内NOS阳性细胞数分别为(5.70±1.30)个/5个视野和(6.19±1.01)个/5个视野]和NOS活性以及NOSmRNA基因表达(灰度测定值分别为28.33±5.50和33.67±6.67)均少于正常对照组NOS阳性细胞数分别为(13.94±2.35)个/5个视野和(17.68±2.76)个/5个视野,灰度测定值分别为52.83±5.19和60.33±8.50](P<0.01)。结论:心肌缺血引起心肌NO浓度的显著下降,其机制可能是缺血引起了NOSmRNA基因表达的减少。

Dynamic changes of the concentration of nitric oxide in ischemic myocardium and its mechanism

AIM: The study was undertaken to explore the dynamic changes of the concentration of nitric oxide(NO) in ischemic myocardium and its mechanism.METHODS: In vivo myocardial ischemia of mice and in vitro perfused isolated heart of rat were used in the experiment. The effects of severity and time of ischemia on NO production, NOS activity and mRNA were examined, respectively. RESULTS: There was a considerable difference (P<0.01) in the concentration of NO between ischemia group (9.12±1.40) μmol/L] and control group (20.16±1.67) μmol/L] after Pit(30 U/kg) administration, and the concentration of NO of ischemic group significantly decreased (9.17±1.33) μmol/L] compared with control group (19.90±1.95) μmol/L] after 30 minutes of ischemia. Also, the concentration of NO after Pit(20 U/L) administration in K-H and 15 min of ischemia was (15.41±2.00) μmol/L and (15.09±2.00) μmol/L respectively in vitro, significantly lower than control group (23.83±2.33) μmol/L and (23.63±2.52) μmol/L]. In addition, compared with control group, the number of NOS positive cells, NOS activity as well as mRNA expression in atrial muscle and ventricular muscle of ischemic group were markedly reduced, respectively. CONCLUSION: Myocardial ischemia could reduced the NO level in myocardium, down-regulation of NOS mRNA could be the possible mechanism.