Changes in nitric oxide level and guanosine monophosphate activity after ischemic preconditioning in diabetes myocardium: in vivo rat hearts / 中华胸心血管外科杂志

ABSTRACT

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 malonyldialdehyde (MDA),superoxide dismutase (SOD) in myocardium were dectected were assessed.In addition,the changes of content of myocardial cGMP and NO were assessed.Ultrathin 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 compared 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 ischemic reperfused rat heart,which may be related with inhibiting of the expression of the NO-cGMP signaling pathway.