Change Of B-type Natriuretic Peptide Expression During Exercise Preconditioning Induced Myocardial Protection In Rat

objective: Repeated of high-intensity exercise can cause heart suffer atimes of myocardial ischemia/hypoxia, which induces a great cardioprotection, knowas “exercise preconditioning (EP)”. EP is an endogenous cardioprotection, and whichhas been an increasingly concerned by researchers. The mechanism of EP has beenimproved, and it not covered by cardiac endocrine. B-type natriuretic peptide is animportant role of natriuretic peptide family. BNP has a great effect, such asvasodilatory, diuretic and natriuretic. In this study, under the background of EP, weexamined the change of BNP in tissues and blood to probe the effects of EP onmyocardial expression of BNP. Then afforded new evidences to EP-inducedcardioprotection and the cellular and molecular mechanisms of EP.Methods:150adult male Sprague-Dawley rats were randomly assigned to6groups. Group C was control. Group EEP was subjected to a high-intensity intervalexercise protocol, as EP model, and rats were killed0.5h after EP. Group LEP wassubjected to the EP protocol, and rats were killed24h after exercise. Group EE runfor3h on the treadmill at35m/min, as sport injury model. Group EEP+HE wassubjected to an EP protocol, and then suffer a sport injury protocol After EP0.5hour.Group LEP+HE was subjected to the EP protocol, and then suffer a sport injuryprotocol after EP24hours. Then the lever of cTnI was detected by chemiluminescentimmunoassay. HE staining was used to observe the changes in ventricular structure.Hematoxylin-basic fuchsin-picric acid (HBFP) staining and Chromotrope2R-Brilliantgreen(C-2R) staining were evaluated the degree of myocardial ischemia/hypoxia. Thechange of BNP in myocardium and plasma were detected by immunohistoChemistryand enzyme inked immunosorbent assay respectively.Results:(1) As compared with the group C, there was no significant difference inthe level of cTnI and the degree of myocardial ischemia/hypoxia in group EEP andgroup LEP, but it has a significant increase in group HE. As compared with group HE,there was a significant decrease in the level of cTnI and the degree of myocardialischemia/hypoxia in group EEP+HE and group LEP+HE. There was no significantdifference between EEP and LEP as well as EEP+HE and LEP+HE.(2) Comparedwith the group C, the expression of BNP in plasma was increased significantly ingroup HE and group EEP, except group LEP. As compared with group HE, the level of BNP in plasma significantly increase only in group LEP+HE, group EEP+HE hasno significant difference. Compared with the group LEP, it has a significant increasein group EEP. Compared with the group LEP+HE, it has a significant decrease ingroup EEP+HE.(3) Compared with the group C, the expression of BNP inmyocardium was increased significantly in group HE, group EEP and group LEP.Compared with group HE, the expression of BNP in myocardium was increasedsignificantly in group EEP+HE and group LEP+HE. To the expression of BNP inmyocardium, there was no significant difference between EEP and LEP as well asEEP+HE and LEP+HE.Conclusion: EP is a non-invasive preconditioning, to protect myocardium frommyocardial damage by high-intensity exercise. Exercise preconditioning can inducemyocardium to produce BNP, and the expressions of BNP have no significantdifference between early exercise preconditioning and late exercise preconditioning.BNP participated in cardioprotective effect of exercise preconditioning and plays animportant role.