| Objective The purpose of this study was to investigate the effects of aerobic exercise on cardiac sympathetic activation and beta-adrenoceptor (p-AR) expression in normal and myocardial infarction rat left ventricles.Method 70 three month old male Sprague-Dawley rats were randomly divided into five groups:control group(C), aerobic exercise group(E), control after myocardial infarction group(MC), aerobic exercise after myocardial infarction group(ME) and sham operation group(SC). Treated with ligating the proximal portion of the left coronary artery or sham operation procedure, after surgery each group survived 12 rats. Throu gh using the treadmill with increased load running training way, an aerobic exercise model of rats was established.8 weeks later, the hemodynamics, heart TTC dyeing and Myocardial specialized dyeing was monitored to reflect heart organization structure and cardiac changes. Left ventricular tissue cardiac sympathetic andβ-AR protein were quantified by Immunochemical streptavidin-biotin complex staining and Western blot analysis, respectively. And discuss the possible biological mechanism. Immunohistochemical and dyeing pictures using Olympus microscope and image analysis system for observation, taking pictures. Add a Western Blot Quant TLv2005 software Image is used by SPSS, the result analysis and processing 17.0 for Windows software package in the statistical processing, the results mean±standard deviation said.Results1 Through myocardial HE and Masson staining observation, myocardial organization structure normal in normal control group and sham operation group rats;myocardial cell hypertrophy, arranging rules, interstitial collagen moderate hyperplasia in aerobic exercise rats;myocardial cells are arranged disorder, interstitial collagen excessive proliferation in myocardial infarction rats;interstitial collagen excessive proliferation improved in aerobics exercise after myocardial infarction rats.2 Aerobic exercise can decreases the weight of normal rats significantly (P<0.01), improves heart weight significantly (P<0.05), improves heart coefficient significantly (P<0.01);weight of myocardial infarction rats increase significantly (P<0.01), heart weight improves significantly (P<0.05), heart coefficient improve significantly (P<0.01); aerobic exercise can significantly reduce weight (P<0.01) and heart weight (P<0.05) but significantly improve heart coefficient in myocardial infarction rats (P<0.01).The results show that aerobic exercise lead to cardiac hypertrophy; myocardial infarction lead to cardiac happen pathologic hypertrophy, aerobic exercise can significantly improve myocardial infarction rats pathological cardiac hypertrophy.3 Comparing with control group, aerobic exercise group heart rate (HR) and left ventricular end diastolic pressure (LVEDP) significantly lower (P<0.01), left ventricular pressure peak (LVSP) and left ventricular pressure maximum climbing speed (±dP/dt Max) significantly increased (P<0.01);in myocardial infarction group, rats HR and LVEDP significant increases, LVSP and±dP/dt Max significantly lower (P<0.01); aerobic exercise after myocardial infarction group, rats HR and LVEDP movement significantly lower, LVSP and±dP/dt Max significantly increased (P<0.01). Aerobic exercise can significantly increase rat T wave voltage (P<0.01), QRS wave group of interphase and QT interphase no significant change; compared with Sham operation group, each index all change significantly in myocardial infarction group rats (P<0.01), performance for T wave voltage drops significantly, QRS wave group of interphase and QT interphase significantly increased; compared with sham operation group, rats QRS wave group of interphase, QT interphase and T wave voltage are no significant differences in aerobic exercise after myocardial infarction group. But compared with myocardial infarction group, rats QRS wave group of interphase and QT interphase significantly (P<0.01), T wave voltage no significant difference in aerobic exercise after myocardial infarction group. The results show that, aerobic exercise can significantly improve the rat heart function; after myocardial infarction rats significantly reduced cardiac function, aerobic exercise can significantly improve heart function of myocardial infarction rats.4 Reflect the distribution of the sympathetic nerves of tyrosine hydroxylase (TH) and growth associated protein-43 (GAP-43) shows the aerobic exercise rats left ventricular TH and GAP-43 protein expression significantly higher than control group (P<0.01);compared with sham operation group, the protein expression of TH significantly lower, but the protein expression of GAP-43 significantly higher in myocardial infarction rats left ventricular (P<0.01);compared with myocardial infarction group, the protein expression of TH significantly higher (P<0.01), but the protein expression of GAP-43 significantly lower (P<0.01) in aerobic exercise after myocardial infarction group rats left ventricular. The results show that, aerobic exercise can significantly increase rats left ventricular sympathetic nerve distribution, promote sympathetic new life; myocardial infarction can significantly reduce rats left ventricular sympathetic nerve distribution, promote sympathetic neurogenesis;aerobic exercise can significantly increase myocardial infarction rats left ventricular sympathetic nerve distribution, reduce the sympathetic neurogenesi.5 Aerobic exercise group rats left ventricular beta 1-AR and beta 3-AR express significant higher than control group (P<0.01);myocardial infarction group rats left ventricular beta 1-AR and beta 3-AR express significantly lower than sham operation group (P<0.01);compared with myocardial infarction group, left ventricular beta 1-AR express significant higher (P<0.01), but beta 3-AR express significant lower (P<0.01) in aerobic exercise after myocardial infarction group. The results show that, aerobic exercise can improved ventricular myocardial infarction rats in beta 1/3-AR balanced by lowering beta 3-AR expression, to realize sympathetic reshape, thereby improving MI rats hearts function.6 Aerobics exercise group rats left ventricular Endothelial nitric oxide synthase (eNOS) express significant higher than control group (P<0.01);myocardial infarction rats left ventricular eNOS express significant higher than sham operation group (P<0.01);aerobic exercise after myocardial infarction group left ventricular eNOS express significant lower than myocardial infarction group (P<0.01). The results show that, aerobic exercise reduces myocardial infarction rats left ventricular beta 3-AR express, causes myocardial infarction rats sympathetic reshape possibly through the change of left ventricular myocardial infarction rats eNOS express realize.ConclusionThis study found that aerobic exercise can cause athletic cardiac hypertrophy, significantly improve rat heart function, make sympathetic nerve distribution increased, stimulate sympathetic nervous moderate hyperplasia, up-regulated beta 1-AR characterization, down-regulated beta 3-AR characterization. So we think aerobic exercise induced heart function enhanced with sympathetic moderate hyperplasia, has close relationship with myocardial cell beta 1/3-AR characterization.This research proves that, MI lead to cardiac function reduce significantly, left ventricular beta 1/2-AR balance reduced, heart positive inotropic function decline; heart beta 3-AR activity has increased significantly, lead to negative muscle function. After myocardial infarction beta 1/3-AR balance changes, produce heart negative muscle function as the net effect, heart only by improving the sympathetic activity, by increasing the heart rate to maintain normal cardiac output, shows that myocardial infarction rats sympathetic has reshape phenomenon, and is related with eNOS expression.This study found that aerobic exercise after myocardial infarction rats can significantly improve heart function, through improving myocardial infarction rats left ventricular beta 1/3-AR characterization, reduce sympathetic neurogenesis, improve sympathetic reshape, enables cardiac autonomic nerve balanced tendency to normal. Beta 3-AR lead to negative muscle function main through activating eNOS. So we presume that, erobic exercise can inhibit beta 3-AR activity by lowering the activity of eNOS express in myocardial infarction rats left ventricular, thereby improving myocardial infarction rats heart function. |
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