Temporal Exercise Conditioning Confers Dual-Phase Cardioprotection Against Isoproterenol-Induced Injury in a Rat Model

Figures

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  Figure 1. Study design. Rats received 3 weeks of forced swim training before and/or after isoproterenol-induced myocardial injury. High-resolution echocardiography was carried out at the endpoint, and ex vivo LAD-ligation was performed on a Langendorff apparatus to evaluate infarct size. Protein assays were carried out on myocardial samples to assess injury-induced changes. Created in Biorender. Dániel Priksz (2025) https://BioRender.com.

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  Figure 2. Infarct size after I/R injury among the treatment groups. Hearts isolated from rats in the different treatment arms were perfused via a Langendorff apparatus, and a 30 min ischemia was induced by the ligation of the LAD, which was followed by 120 min reperfusion. Hearts were then stained with TTC and the infarcted tissues were determined in 2 mm thick sections as a function or the total area at risk. The infarct size was significantly increased in the ISO group (red) compared to control, and was attenuated by the PRE + ISO + POST (green) and ISO + POST (brown) groups compared to ISO. **** p < 0.0001, ** p < 0.01, * p < 0.05.

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  Figure 3. Endpoint echocardiographic parameters of treatment groups. (A) LA size increased in ISO but decreased in all treatment groups; PRE + ISO + POST treatment normalized LA size most effectively. (B) Ejection fraction was reduced in ISO and improved significantly in both PRE + ISO and PRE + ISO + POST groups. (C) Stroke volume decreased in ISO and was partially restored in PRE + ISO + POST, while PRE + ISO and ISO + POST showed lesser improvement. (D) MAPSE was diminished in ISO and fully normalized by PRE + ISO + POST; PRE + ISO and ISO + POST provided partial restoration. (E) LVOT mean velocity decreased in ISO, with PRE + ISO + POST and ISO + POST showing marked recovery compared to PRE + ISO. (F) Tei index increased in ISO and was significantly reduced in PRE + ISO + POST and ISO + POST, with PRE + ISO having a more pronounced effect. (G) MV E/A ratio was not significantly different among groups. (H) MV deceleration time slightly shortened in ISO, while PRE + ISO, PRE + ISO + POST, and ISO + POST all normalized DecT, with PRE + ISO + POST demonstrating the greatest effect. (I) IVCT was prolonged in ISO and improved in PRE + ISO + POST, with partial improvement in the PRE + ISO and…

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  Figure 4. (A) Heme-oxigenase-1 (HO-1) concentration significantly decreased in myocardial samples of ISO-treated rats, while it was restored in all treatment groups, reaching the highest expression in the PRE + ISO +POST group (B) The enzyme activity of HO-1 dramatically decreased in the diseased group, but increased after the pre-and post-treatments, reaching the highest activity in the PRE + ISO + POST animals. (C) Myeloperoxidase (MPO) activity increased in ISO, but decreased in all treatment groups. One-way ANOVA with Tukey’s post hoc test was used to evaluate differences among groups; *: p < 0.05; **: p < 0.01; ***: p < 0.001; ****: p < 0.0001.