The Expression of TNF-α in Cardiac Conduction System after Exhaustive Exercise and Their Role in Exercise Induced Arrhythmia

Objective:To discuss the gene and protein expression characters of TNF-α of cardiac sinus node, atrioventricular node and Purkinje fibers at different time-phrase after exhaustive exercise, providing experimental evidence for clarifying the mechanism of exercise-induced arrhythmia.Method:100 healthy adult male SD rats were grouped into 10 groups (10 rats for each group) as 4 groups of one-time exhaustive swimming group (n=40) , 4 groups of 2-week repeated exhaustive swimming group (n=40) and 2 control groups (n=20) .Rats were sacrificed at 0, 4, 12, and 24 hours after exhaustive swimming, then Laser microdissection (LMD) and immune fluorescent histochemical were underwent according to time-phrase.The SAN, AVN and Purkinje's fiber cells were spotted and collected in the approach of Laser Microdissection (LMD) .The mRNA and protein expression of TNF-α on the SAN, AVN and Purkinje's fiber cells were analyzed by real-time fluorescent quantitative PCR, immunochemistry and image analysis.Results:Compared to control group, the expression of mRNA and protein of TNF-α on cardiac sinoatrial node and atrioventricular node increased greatly immediately after two exhaustive exercise (P<0.01) .The expression of mRNA and protein of TNF-α on cardiac Purkinje fiber dropped markedly 4 hours after one-time exhaustive exercise (P<0.01) .The expression of mRNA and protein of TNF-α on heart conduction system declined significantly after repeated exhaustive exercise, especially at 12 hours after exercise on sinoatrial node and atrioventricular node and 24 hours on Purkinje's fiber cells (P<0.01) .Conclusion:After one-time exhaustive exercise, the mRNA and protein of TNF-α greatly expressed on sinoatrial node and atrioventricular node, causes inflammation and proliferation on fiber cells, leading to the cardiac sinus pacing and sinus electrical conduction abnormalities, which is one of the factors of arrhythmia.Repeated exhaustive exercise causes irreversible damage on cardiac conduction system, and the mRNA and protein of TNF-α on heart conduction system expressed at low level and no significant change has tested.