[Effects of different intensity exercise on morphology and structure of atrioventricular node and protein expressions of VEGF, VIP and Syn in rats].

To investigate the effects of different intensities of aerobic exercise on the morphology of the atrioventricular node and the expressions of vascular endothelial growth factor (VEGF), vasoactive intestinal peptide (VIP) and synaptophysin (Syn) in rats. Three-month-old SD rats were randomly divided into 3 groups: quiet control group (C), moderate-intensity aerobic exercise group (AE), and high-intensity aerobic exercise group (FE), each with 8 rats. The moderate-intensity aerobic exercise and high-intensity aerobic exercise rat models were rats established by using 8-week treadmill training ways. Compared with the quiet control group, in the moderate-intensity aerobic exercise group, the atrioventricular nodule muscle fibers were evenly distributed, with smaller gaps, a sense of transparency, and collagen tightly wraps around the atrioventricular nodules. The intercalary disc had a clear structure and complete connection, and the capillary tube wall was relatively clear. Thick elastic fibers were more developed, the expression levels of VEGF and VIP in the atrioventricular node were increased significantly (＜0.05), and there was no significant change in the expression of Syn. In the high-intensity aerobic exercise group, the atrioventricular nodule muscle fibers were unevenly distributed and arranged abnormally, connection between cells were disordered, and vacuolated. The intercalary disk was twisted, circling and overlapping, fuzzy, discontinuous, and extremely dilated. The wall was thick and the endothelial cells were arranged sparsely and disorderly. Moreover, high-intensity aerobic exercise significantly inhibited the expressions of VEGF, VIP, and Syn (＜0.05). Aerobic exercise training of different intensities has obvious effects on the morphology and structure of the atrioventricular node and the expressions of VEGF, VIP and Syn. Moderate aerobic exercise can maintain and promote the normal morphology and structure of the atrioventricular node, while high-intensity aerobic exercise can damage the morphology and structure of the ventricular node, which is presumably closely related to the arrhythmia induced by high-intensity exercise.