| Objective:Cardiac troponin I (cTnI), as one of markers measuring myocardial injury in the high specificity and high sensitivity, has its unique advantages on the detection of myocardial injury in sports. Hematoxylin-eosin (HE) staining not only can show the basic structure of tissue, but also show the morphological changes of myocardial ischemia and hypoxia. Hematoxylin basic fuchsin picric acid (HBFP) staining is a morphological indicator of the early myocardial ischemia and hypoxia. At present, the application of the three methods above have been reported in many studies, but the relevant study on serum cTnI and HBFP staining has not been reported, and the comparative studies on HE staining and HBFP staining has been no reported, either. Therefore, this study adopts the methods of high-intensity intermittent exercise induced myocardial preconditioning, exhaustive exercise induced myocardial injury in sports, isoproterenol drug-induced myocardial injury, through detecting changes in serum cTnI levels, combined with the morphology characteristics of HE staining and HBFP staining in the myocardial tissuem, to conduct the comparative study on the different degrees of experimental myocardial injury. The aim of this work is to research the relationship of Serum cTnI and myocardial injury morphology, providing an updated theoretical and experimental basis for exercise myocardial injury and protective effect.Methods:In this study,60 healthy male SD rats were randomly divided into four groups:control group (C), exercise preconditioning group (EP), exhaustive exercise group (EE) and isoproterenol group (ISO). C group with conventional feeding, without any other treatment; EP group with high-intensity intermittent exercise induced myocardial preconditioning; EE group with an exhaustive exercise induced myocardial injury; ISO group using intraperitoneal injection with large doses of drug induced myocardial injury. Chemiluminescent immunoassay to detect changes of serum cTnI levels, HBFP and HE staining to detect myocardial ischemia and hypoxia changes, using computer image analysis technology conducts quantitative study on HBFP stained hypoxic area and integral optical density, and the correlation study on serum cTnl levels and the HBFP staining hypoxic area. Results:1.Serum cTnI levels:Serum cTnI levels were 0.02±0.01 ug/ml in group C,0.05±0.03 ug/ml in group EP,46.08±37.41 ug/ml in group EE, 35.75±26.00ug/ml in group ISO. Compared with group C, serum cTnI level in group EP increased slightly, but not significantly; Serum cTnI level in group EE was significantly high (P<0.05); serum cTnI level in group ISO was also significantly high (P<0.05). However, there was no difference between group EE and group ISO.2.HE staining:Myocardium in group C and group EP were well arranged in net-shape, and even dyeing with clear outline and red staining in cytoplasm; the oval-shaped blue nucleus were located at cell center. Myocardium in group EE and group ISO were disrupt, wave-shaped and swollen with unclear outline and uneven staining in plasm, and enhanced acidophilic red staining sometimes.3.HBFP staining: Myocardium in group C and group EP were yellow-brown staining and well arranged with clear outline which showed normal cells without hypoxia and ischemia. Myocardium in ischemia in group C and group EP were red staining, blot or piece shaped, most seen in endocardium, septum interventriculare and papillary muscle. HBFP image analysis:Myocardium in group C demonstrated no hypoxia and ischemia staining, Myocardium in group EP showed blot-shaped staining. Compared with group C, area of hypoxia and ischemia and Integral optical density in group EP were slightly high, but not significantly. The area of hypoxia and ischemia in group EE was 1865.5±1129.9μm2, Integral optical density was 475710±288121. The area of hypoxia and ischemia in group ISO was 1373.6±767.0μm2, Integral optical density was 350270±195587. Compared with group C, area of hypoxia and ischemia and Integral optical density in group EE and group ISO were significantly high (P<0.05), however, there was no difference between group EE and group ISO.5.The relationship between serum cTnI level and area of hypoxia and ischemia in HBFP staining:There was a positive correlation between serum cTnI level and area of hypoxia and ischemia. Coefficient between area of hypoxia and ischemia by HBFP staining in group EP was r=0.801 (P<0.05). Coefficient between area of hypoxia and ischemia by HBFP staining in group EE was r=0.805 (P<0.05). Coefficient between area of hypoxia and ischemia by HBFP staining in group ISO was r=0.890 (P<0.05).6.Comparative study between HE and HBFP staining:HE and HBFP staining with adjacent section showed that when myocardial injury occurred, enhanced acidophilic red staining was located where hypoxia and ischemia staining displayed. Conclusion:1.As a sensitive biomarker, serum cTnI level can be used to detect the injury of the exhaustive exercise and ISO induced myocardial injury in rats, and one single bout of high-intensity interval exercise exerts no injury to the heart.2.When the myocardial injury occurred, there is a positive correlation between the serum cTnI level and the ischemic and hypoxic area demonstrated by HBFP staining.3.The enhanced acidophilic stain of cells by HE staining are well correlated with the ischemic and hypoxic area displayed by HBFP staining, using two methods together may evaluate myocardial ischemic and hypoxic alteration in an all-round manner.
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