Objective    To investigate the changes of tumor necrosis factor-α(TNF-α) and  its role  in myocardial insulin resistance (IR) during cardiopulmonary bypass(CPB) in dogs.     Methods    Twelve mongrel dogs undergoing CPB were equally divided into 2 groups at random: groupⅠ

  recelving aortic cross-clamping  for 30 min and group Ⅱ

aortic cross-clamping for 120 min. The plasma concentrations of glucose

insulin

TNF-α and the change of insulin resistance index(IRI) were detected before CPB

reperfusion for 15 min

45 min and 75 min

respectively.     Results    After myocardial ischemia-reperfusion

the plasma concentrations of glucose

insulin and  IRI  were all significantly increased and reached their peak levels during reperfusion for 15 min and 45 min in comparison with pre-bypass levels (P0.05) . Meanwhile there was severe dysfunction in myocardial glucose uptaking and utilization. In comparison with group I

the increased degree of those indexes was more obvious and lasted longer time in groupⅡ. After ischemia reperfusion

TNF-α  increased obviously

reached their peak points 15 min after being declamped

and remained a high level within 75 min as compared with pre-bypass (P0.05).Compared with groupⅠ

the rise of TNF-α in groupⅡ was more evident and lasted longer.     Conclusion    The phenomenon of myocardial insulin resistance exists after myocardial ischemia-reperfusion during extracorporeal circulation. TNF-α plays an important role in myocardial insulin resistance undergoing cardiopulmonary bypass.