Objective:To investigate the effect of exogenous tumor necrosis factor alpha(TNF-α) on muscle ring finger-1(MuRF-1) in rat heart.Methods:Left anterior descending(LAD)coronary artery ligation was used to build myocardial infarction(MI) animal model.40 adult Sprague-Dawley rats were randomly divided into 4 groups:①MI+TNF-α group

in which LAD was ligated and TNF-α was injected 100 ng/(g·d)(in 2 ml 0.9% saline) via intraperitoneal(i.p.) route.②MI group

in which rats received 2 ml normal saline i.p.injection after LAD ligation.③Sham+TNF-α group

in which after sham operation was performed

rats was given i.p.injection of TNF-α100 ng/(g·d)(in 2 ml 0.9% saline).④Sham group

in which sham-operated rats served as controls

and also received 2 ml normal saline i.p.injection.All i.p.injections were performed for 7 consecutive weeks.After harvesting the hearts

morphology and ultrastructure of left ventricles were measured.The MuRF-1 gene level was determined by quantitative real-time PCR and its protein level was evaluated by Western blot.Results:The histology and ultrastructure of left ventricles showed that cardiac lesion was worsened and there were much more infiltration of inflammatory cells in MI+TNF-α group as compared with MI group and Sham+TNF-α group.The pathology results also showed that there were increased cardiac muscle fiber broken nucleolus cleavage

much more mitochondria hyperplasia and vacuole in MI+TNF-α group.The mRNA and protein levels of MuRF-1 were 1.81±0.8 and 0.9±0.25 in MI group

534±0.96 and 1.12±0.76 in Sham+TNF-α group.They were prominently increased compared with Sham group(0.84±0.2 and 0.27±0.15;P<0.05).Compared with MI group

the mRNA level and protein expression of MuRF-1 in MI+TNF-α group were further augmented(3.6±1.5 and 1.71±0.23

respectively;P<0.05 and P<0.01).Conclusion:Exogenous tumor necrosis factor alpha up-regulates the expression of muscle ring finger-1 in rat heart and plays a very important role in myocardial injury.