|（1.School of Physical Education，Xizang Minzu University，Xianyang 712082，China；2.Exercise＆Cardiovascular Lab，Institute of Sports and Exercise Biology，Shaanxi Normal University，Xi’an 710062，China)
Abstract: In order to probe into the roles of the changing of cardiac β2-AR/β1-AR in exercise alleviating myocardial fi-brosis after myocardial infarction, the authors divided 36 male SD rats randomly into a sham surgery group (S), a myocar-dial infarction group (MI), and an aerobic exercise after myocardial infarction group (ME), each of which consisted of 12 rats, established a MI mode on the rats in group MI by means of ligation of the left anterior descending (LAD) coronary artery, stitched but not ligated the LAD of the rats in group S, let the rats in group ME exercise on a treadmill for 4 weeks, 1 week after MI, according to the following plan: week 1: adaptive training (speed: 10m/min, gradient: 0%); week 2: speed: 15mmin, gradient: 3%; week 3: speed: 20m/min, gradient: 3%; week 4: speed: 25m/min, gradient: 5%; total exer-cise time: 60min, training: 5 days a week, 4 weeks consecutively. After the training was finished, the authors opened the rats’ chest and took out their hearts, measured left ventricular β2-AR protein expression by means of immunohistochemis-try, measured left ventricular Nox4 expression by means of fluorescent immunohistochemistry, measured β1-AR, β2-AR and Nox4 protein levels by means of Western Blot, measured myocardial superoxide anion level by means of DHE, meas-ured myocardial collagen volume fraction (CVF) by means of Masson staining, and revealed the following findings: as compared with the rats in group S, the rats after MI could be seen having myocardial β2-AR and Nox4 positive staining, large areas of superoxide anion red fluorescence and blue myocardial collagen fibers; in LV after MI, the radio of β2-AR/β1-AR increased significantly (P<0.01), myocardial Nox4 protein expression, superoxide anion level and CVF value increased significantly (P<0.05, P<0.01, P<0.01); as compared with the rats in group MI, the rats in group ME could be seen having myocardial β2-AR and Nox4 positive staining, but significantly decreased superoxide anion red fluores-cence and blue collagen fibers; in LV after exercise, the radio of β2-AR/β1-AR was down-regulated significantly (P<0.01), myocardial Nox4 protein expression, superoxide anion level and CVF value decreased significantly (P<0.05, P<0.05, P<0.01); and in LV, β2-AR/β1-AR was significantly positive correlative with myocardial CVF (r=0.419, P<0.05). The said findings indicate the followings: aerobic exercise can down-regulate the ratio of left ventricular β2-AR/β1-AR, restrain the pathway of Nox4-ROS, and alleviate the degree of myocardial fibrosis of rats with myocardial infarction; exercise is re-lated to the restraint of myocardial fibrosis and the decrease of the ratio of β2-AR/β1-AR after myocardial infarction.
Key words: sports physiology；β2-AR/β1-AR；myocardial fibrosis；myocardial superoxide anion；aerobic exercise；myocardial infarction；rats