Objective:To study the NF-κB p65 expression of the myocardium with different pressure cardioplegia perfusion in rat hearts in order to find the new way for myocardial protection on cardiopulmonary bypass.Methods:Thirty of Sprague Dawley rats were divided into three groups randomly:the control group

low pressure group and high pressure group.Control group:the normal myocardial samples were collected for study.Low pressure group:the hearts were perfused with a 4℃ St.Thomas’ cardioplegia solution at the pressure of 50 mmHg for 5 minutes

then the myocardial samples were collected for study.High pressure group:the hearts were perfused with a 4℃ St.Thomas’ cardioplegia solution at the pressure of 100 mmHg for 5 minutes

then the myocardial samples were collected for study.The NF-κB p65 expression of the myocardium were measured respectively by immunohistochemical staining and Western blotting.Results:Integrated optical density(IOD) was measured by immunohistochemical.Control group:there was some expression of NF-κB p65(80.1±9.10).High pressure group:the expression of NF-κB p65 was observed in the myocardium(226.7±12.5).Low pressure group:the expression of NF-κB p65 was observed in the myocardium too(117.5±15.5)

but the density level was obviously lower than high pressure group(P<0.05).The relative optical density was detected by Western blot analysis.Control group:there was some expression of NF-κB p65(0.44±0.05).High pressure group:the expression of NF-κB p65 was observed in the myocardium(1.58±0.13).Low pressure group:the expression of NF-κB p65 was observed in the myocardium too(0.95±0.05)

it was significantly lower than high pressure group(P<0.05).Conclusion:The results suggest that there were different degree expression of NF-κB p65 with different pressure cardioplegia perfusion

but the low pressure cardioplegia perfusion was better than high pressure in myocardial protection.