缺血预处理对糖尿病在体大鼠心肌环磷酸腺苷及环磷酸腺苷依赖蛋白激酶表达的影响

Effect of ischemic precondition on the expression of cyclic adenosine monophosphate and cAMP-dependent protein kinase A in myocardium of diabetic rats in vivo

目的探讨糖尿病大鼠心肌缺血预处理(IPC)后环磷酸腺苷(cAMP)及环磷酸腺苷依赖蛋白激酶(PKA)表达的变化。方法选取糖尿病与非糖尿病SD大鼠各30只,分为3组(n=10):假手术(Sham)组,缺血再灌注(I/R)组及IPC组。比较各组血清肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)、心肌梗死面积(MI)及心肌cAMP、PKA含量的变化。电镜标本观察心肌线粒体。结果非糖尿病大鼠中,IPC组与I/R组比较,CK减少[(2428.32±170.19)vs(6324.06±356.26)U/L,P<0.05],LDH减少[(1698.98±129.65)vs(4660.15±115.34)U/L,P<0.05],CK-MB减少[(1450.43±23.56)vs(3280.90±71.33)U/L,P<0.05],MI减少[(5.63±9.32)%vs(17.75±7.36)%,P<0.05]。糖尿病大鼠中,IPC组与I/R组比较,CK、LDH、CK-MB、MI未见明显缩小[(5962.63±145.22)vs(6012.13±124.08)U/L,(5998.44±123.40)vs(6023.54±89.01)U/L,(4011.13±81.09)vs(4380.71±76.21)U/L,(13.54±2.39)%vs(15.25±4.33)%,P>0.05]。非糖尿病大鼠中,IPC组与I/R组比较,cAMP增加[(0.61±0.07)vs(0.32±0.06)pmol/g,P<0.05],PKA含量增加[(17.05±1.75)vs(12.68±1.13)pmol/(mg·min),P<0.05],糖尿病大鼠IPC组cAMP、PKA含量无明显增加[(0.35±0.04)vs(0.37±0.08)pmol/g,(12.14±2.15)vs(11.79±1.16)pmol/(mg·min),P>0.05]。非糖尿病大鼠IPC组线粒体的损伤减轻,而糖尿病大鼠IPC组线粒体损伤未见减轻。结论非糖尿病大鼠IPC可保护心肌。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cAMP信号系统表达受抑制有关。

Objective To study the changes of the cyclic adenosine monophosphate （cAMP） and protein kinase A （PKA） expression in myocardium of diabetic rat after ischemic preconditioning （IPC）.Methods Thirty diabetic and thirty non-diabetic SD rats were divided into 3 groups （n=10,each） randomly：control group（Sham group）,IPC group and ischemia/reperfusion group（I/R group）.At the end of the experiment,the changes of activity of the serum creatine kinase （CK）,creatine kinase isoenzyme （CKMB） and lactate dehydrogenase （LDH） were detected.And the scope of myocardial infarction（MI） and the changes of content of myocardial cAMP and protein kinase A（PKA） were also assessed.Ultrathin sections of 70 nm thick were made and transmission electron microscopy was used to detect the structure of the mitochondria.Results Compared with I/R group,myocardial enzymes leakage and MI size were significantly reduced in IPC group of non-diabetic rats [CK,（2428.32± 170.19） vs （6324.06±356.26）U/L,P＜0.05; LDH,（1698.98±129.65） vs （4660.15±115.34） U/L,P＜0.05; CK-MB,（1450.43±23.56）vs （3280.90±71.33） U/L,P＜0.05; MI size,（5.63±9.32）％ vs （17.75±7.36）％,P＜0.05],and cAMP [（0.61 ±0.07） vs （0.32±0.06）pmol/g],PKA [（17.05± 1.75） vs（12.68± 1.13）pmol/（mg · min）] were also significantly increased （P＜0.05）.But there was no significant myocardial protective effect in diabetic rats [CK,（5962.63±145.22） vs （6012.13±124.08） U/L,LDH （5998.44±123.40） vs （6023.54±89.01）U/L,CK-MB,（4011.13±81.09） vs （4380.71±76.21） U/L,MI size,（13.54±2.39） ％ vs （15.25±4.33） ％,P＞0.05].cAMP and PKA were not significant increased in diabetic rats [cAMP,（0.61 ± 0.07） vs （0.32 ± 0.06） pmol/g,PKA,（12.14 ± 2.15） vs （11.79 ± 1.16）pmol/（mg· min）,P＞0.05].The destruction of the mitochondria were decreased in IPC group in non-diabetic rats,but not in diabetic rats.Conclusion Diabetes inhibits the protective effect of ischemic preconditioning on ischemic reperfusion rat heart,which is related with inhibiting the expression of myocardial cAMP.