Abstract: Objective:To explore the cardiac muscle be affected by PI3K in the course of tapering and its mechanism. Methods: 72 male SD rats were randomly divided into 8 groups after one week of adaptability training:the group that rest for 3 weeks (C3), the group that receive large amount of training for 3 weeks (E3); the group that rest for 3 days (C4)and the group that receive 3 days of tapering (E4);the group that rest for 6 days (C5) and the group that receive 6 days of tapering (E5); the group that rest for 2 weeks (C6) and the group that receive 2 weeks of tapering (E6). After 3 weeks of large amount of training and 2 weeks of tapering, the cardiac muscle of left ventricle was sampled. PI3K p85, PI3K p110α and PI3K p110γ protein was tested through Western blotting. The morphological structure of cardiac muscle organization was HE colored and observed under light microscope. Results: After 3 weeks of large amount of training and 2 weeks of tapering, no significant change occurred in the conformation of cardiac muscle organizations. No injuries were observed in the cardiac muscles. PI3K p110α protein expression increased significantly in cardiac muscles after 6 days of tapering (P<0.05). PI3K p110γ didn’t change significantly after 3 weeks of large amount of training and after tapering (P>0.05). Conclusions: The training and tapering in the project didn’t result in any injuries of the cardiac muscles. Cardiac muscles can be affected by tapering through PI3K.

Key words: Tapering, Cardiac Muscle, PI3K p85, PI3K p110α, PI3K p110γ