Objectives  To explore the effect of heavy load exercise on the mitophagy protein expression of PINK1 and Parkin in skeletal muscle of rats, and to analyze the role of PINK1/Parkin pathway in exercise-induced mitochondrial damage in skeletal muscles.

  Methods  Forty-eight male adult SD rats were randomly divided into quiet control group (C group, n=8) and exercise group (E group, n=40).Among them, E group was further divided into 0 h, 12 h, 24 h, 48 h and 72h sub-groups(n=8) according to the time point.Rats in the E group performed a running on a treadmill down a 16° incline at 16m/min for 90 min, and at each time point the soleus muscle was collected under anesthesia.Mitochondrial ultrastructural changes in skeletal muscle were observed by a transmission electron microscope.The content of quantitative enzyme citrate synthase(CS) was measured by ELISA; Protein expression of skeletal muscle PINK1 and mitochondrial Parkin and LC3 were detected by Western blot.

  Results  After heavy load exercise, the mitochondrial structure appeared the typical abnormal changes such as swelling and accumulating under cell membrane, and formed a large number of mitophagosomes which were in different stages of maturity.The content of CS was significantly decreased, and the protein expression of PINK1, Parkin and LC3 were significantly elevated (P < 0.05 or P < 0.01).

  Conclusion  After a heavy load exercise, the structure and quantity of mitochondria in skeletal muscle were impaired, and a large number of mitophagosomes were formed.The mechanism of skeletal muscle damage caused by heavy load exercise may be related to the activation of PINK1/Parkin pathway and the further initiating overactive mitophagy.