缺血预处理对糖尿病大鼠在体心肌NO—cGMP表达的影响

Changes in nitric oxide level and guanosine monophosphate activity after ischemic preconditioning in diabetes myocardium： in vivo rat hearts

目的通过糖尿病大鼠心肌在缺血预处理（IPC）后环磷酸鸟苷（cGMP）及一氧化氮（NO）、一氧化氮合酶（NOS）表达的变化，探讨糖尿病抑制IPC心肌保护作用的机制。方法取糖尿病及非糖尿病SD大鼠各30只，各分为3组（每组10只）。（1）假手术组（Sham组）：开胸后穿线做套环，但不收紧结扎线；持续155min，全程旷置作为基础对照。（2）缺血再灌注组（I／R组）：穿线平衡35min后，持续收紧结扎造成缺血30min，放松后再灌注90min。（3）IPC组：穿线平衡35min后，缺血5min，再灌注5min，反复3次，而后重复I／R组操作。比较各组血清肌酸激酶（CK）、肌酸激酶同工酶（CK—MB）及乳酸脱氢酶（LDH）的变化，心肌组织丙二醛（MDA）含量和超氧化物岐化酶（SOD）活性及心肌组织cGMP、NO、NOS含量的变化。电镜标本行线粒体Flameng评分。结果非糖尿病IPC组与I／R组比较，心肌酶漏出明显减少，MDA含量明显降低，SOD含量明显增加，线粒体损伤明显减轻，cGMP、NO、NOS含量明显增加（P〈0．05）；而IPC在糖尿病大鼠未表现出明显心肌保护作用，cGMP、NO、NOS含量无明显增加（P〉0．05）。结论糖尿病抑制IPC的心肌保护作用，其机制可能与糖尿病大鼠心肌NO—cGMP通路表达受抑制有关。

Objective To study the changes of nitric oxide （NO） , guanosine monophosphate（cGMP） and nitric oxide synthase （NOS） expression of diabetic rat heart after ischemic preconditioning （IPC） , and to explore the possible mechanism of diabetes mellitus inhibiting myocardial protection of IPC. Methods Thirty diabetic SD rats and thirty non-diabetic SD rats were divided into 3 groups （ n = 10 ） randomly. Control group （ Sham group, n = 10 ）, After surgery, no procedures were made; After 155 min, the experiment was ended. Ischemic preconditioning group （IPC group, n = 10） , the rats were subjected three cycles of five minutes of ischemia followed by five minutes of-reperfusion and then subjected to 30 minutes of ischemia followed by 90 minutes of reperfusion. Ischemia/reperfusion group（ I/R group, n = 10 ）, after surgery, the rats were balanced for 35 minutes and then subjected to 30 minutes of ischemia followed by 90 minutes of reperfusion. At the end of the experiment, the hearts of each group were excided quickly, frozen in liquid nitrogen and stored at 80 ℃ until membrane and cytoplasm preparation. The changes of activities of the serum creatine kinase （CK） , creatine kinase isoenzyme （CK-MB） and lactate dehydrogenase （LDH） were detected. The activity of malonyldialdeh）;de （MDA） , superoxide dismutase （SOD） in myo- cardium were dectected were assessed. In addition, the changes of content of myocardial cGMP and NO were assessed. Ultra- thin sections 70 nm thick was made and transmission electron microscopy was used to detect the structure of the mitochondria with the Flameng scoring system. Results Myocardial enzyme leakage and mitochondria injury were significantly reduced com- pared IPC group and I/R group in non-diabetic rats, and cGMP, NO and NOS were also significantly increased （P 〈 0.05 ）. There did not show significant myocardial protective effect in diabetic rats, cGMP. NO and NOS showed also no significant increase in diabetic rats （ P 〉 0.05 ）. Conclusion Diabetes inhibited the protective effect of ischemic preconditioning on ischeuric reperfused rat heart, which may be related with inhibiting of the expression of the NO-cGMP signaling pathway.