Late cardioprotection of exercise preconditioning against exhaustive exercise-induced myocardial injury by up-regulatation of connexin 43 expression in rat hearts

Objective: To investigate the expression of myocardium connexin 43 (Cx43) in late exercise preconditioning (LEP) cardioprotection. Methods: Eight-week-old adult male Sprague Dawley rats were randomly assigned into four groups (n=8). Myocardial injury was judged in accordance with serum levels of cTn I and NT-proBNP as well as hematoxylin basicfuchsin picric acid staining of myocardium. Cx43 mRNA was detected by in situ hybridization and qualified by real-time fluorescence quantitative PCR. Cx43 protein was localized by immunohistochemistry and its expression level was determined by western blotting. Results: The LEP obviously attenuated the myocardial ischemia/hypoxia injury caused by exhaustive exercise. There was no significant difference of CA:113 mRNA level between the four groups. Cx43 protein level was decreased significantly in group EE (P<0.05). However, LEP produced a significant increase in Cx43 protein level (P<0.05), and the decreased Cx43 protein level in exhaustive exercise was significantly up-regulated by LEP (P<0.05). Conclusions: LEP protects rat heart against exhaustive exercise-induced myocardial injury by up-regulating the expression of myocardial Cx43.