Exercise Preconditioning Plays a Protective Role in Exhaustive Rats by Activating the PI3K‐Akt Signaling Pathway

Figures

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  Figure 1. EP provides protective effects on myocardial structure of exhausted rats. Con: sedentary control group; EE: exhaustive exercise group; EP: exercise preconditioning group; EP + EE: exercise preconditioning + exhaustive exercise group; LY + EP + EE : LY294002 (PI3K inhibitor) + exercise preconditioning + exhaustive exercise group; LY: LY294002 group. (a) Light microscopy showed changes in myocardial microstructure among the six groups. Original magnification was ×400. Images showed disorganization and breakage of myocardial fiber, cardiomyocytes degeneration and necrosis, and interstitial substance with edema in the EE group. The LY + EP + EE group and the EP + EE group showed EE-like microstructure damages, but the EP + EE group was slighter. The EP group showed that myocardial fibers were organized, thickened, and slightly swollen. Con and LY groups showed normal myocardial microstructure. (b) Transmission electron microscopy showed changes in myocardial ultrastructure. Magnification was ×15 K; bar = 1.0 μm. Con and LY groups showed normal myocardial ultrastructure. The EP group showed that mitochondria were slightly swollen morphologically. The EE group myocardial fibers…

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  Figure 2. EP reduced the level of CK-MB and cardiac troponin I (cTn-I) in serum of exhausted rats (x ± s, n = 6). (a) The serum level of CK-MB in each group determined by ELISA. (b) The serum level of cTn-I in each group indicated by ELISA. For groups, see the footnote in Figure 1. ∗P < 0.05 compared with the Con group. #P < 0.05, EP + EE group compared with the EE group. ΔP < 0.05, LY + EP + EE group compared with the EP + EE group.

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  Figure 3. Original recording showing the pressure-volume loops. 0the footnote in Figure 1. Compared with the Con group, the EE group, EP + EE group, and LY + EP + EE group showed reduced SV along with increased Ves and increased Ved; thus, the position of P-V loops shifted to the right and the EP group showed decreased Ves and decreased Ved; thus, the position of P-V loops shifted to the left.

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  Figure 4. EP reduced the cardiomyocyte apoptosis in the myocardium of exhausted rats (x ± s, n = 6). The apoptosis of cardiomyocyte was detected by TUNEL. Original magnification was ×400. For groups, see the footnote in Figure 1. (a) TUNEL staining showed the normal cells in blue and the positive cells in green. Few green stains in the Con, EP, and LY groups were observed. In the EE, EP + EE, and LY + EP + EE groups, a significant portion of the tissues were stained green. (b) EP reduced the apoptosis index (AI) in the myocardium of exhausted rats. AI was the percentage of positive cells in the total number of cells. ∗P < 0.05 compared with the Con group. #P < 0.05, EP + EE group compared with the EE group. ΔP < 0.05, LY + EP + EE group compared with the EP + EE group.

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  Figure 5. EP reduced the open level of myocardial mitochondrial permeability transition pore (mPTP) in the myocardium of exhausted rats (x ± s, n = 6). For groups, see the footnote in Figure 1. ∗P < 0.05 compared with the Con group. #P < 0.05, EP + EE group compared with the EE group. ΔP < 0.05, LY + EP + EE group compared with the EP + EE group.

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  Figure 6. The effect of EP on the levels of p-PI3K, p-Akt, Bad, Bax, Bcl-2, and caspase-3 proteins in the rat myocardium after EE (x ± s, n = 6). For groups, see the footnote in Figure 1;(a) original recording showing the p-PI3K and p-Akt. (b) The ratio of p-PI3K/β-actin levels in the rat myocardium. (c) The ratio of nuclear p-Akt/β-actin levels in the rat myocardium. (d) Original recording showing the Bcl-2, Bad, Bax and caspase-3. (e) The ratio of Bcl-2/β-actin levels in the rat myocardium. (f) The ratio of Bad/β-actin levels in the rat myocardium. (g) The ratio of Bax/β-actin levels in the rat myocardium. (h) The ratio of caspase-3/β-actin levels in the rat myocardium. ∗P < 0.05 compared with the Con group. #P < 0.05, EP + EE group compared with the EE group. ΔP < 0.05, LY + EP + EE group compared with the EP + EE group.