Alterations of Cardiac K ATP Channels and Autophagy Contribute in the Late Cardioprotective Phase of Exercise Preconditioning.

The cardiac effects of exercise preconditioning (EP) are well established; however, the mechanisms involving cardiac ATP-sensitive potassium channel (KATP channel) subunits and autophagy are yet to be fully established. The present work aims to investigate the alterations of cardiac KATP channel subunits Kir6.2, SUR2A, and autophagy-related LC3 during the late cardioprotective phase of EP against exhaustive exercise-induced myocardial injury. Rats run on treadmill for four running time intervals, each with 10 minutes running and rest. Exhaustive exercise was performed 24 h after EP. Cardiac biomarkers, cTnI and NT-proBNP, along with the histological stain, were served as indicators of myocardial injury. Cardiac KATP channel subunits Kir6.2 and SUR2A were analyzed in this study, and autophagy was evaluated by LC3. The results revealed that EP reduced the exhaustive exercise-induced high level of serum cTnI and myocardial ischemia/hypoxia; however, it did not reveal any changes in the serum NT-proBNP level or cardiac BNP. Cardiac SUR2A mRNA significantly upregulated during the exhaustive exercise. The high levels of Kir6.2, SUR2A, LC3IIpuncta and LC3II turnover observed after exhaustive exercise were significantly mitigated by EP in the late phase. These results suggest that EP alleviates myocardial injury induced by exhaustive exercise through the downregulation of cardiac KATP channels and autophagy.