| Objective: To investigate the effects of treadmill exercise at different intensity level on endothelial function in spontaneously hypertensive rats(SHR). Methods: Three-month old SHR and WKY were applied in experiments, and were randomly assigned to six groups: sedentary control group(SHR-C, WKY-C), moderate exercise group(SHR-M, WKY-M), and high exercise group(SHR-H, SHR-H). Speed velocity, according to the percent of maximum oxygen update, was 18-20m/min(55-65%VO2max) in moderate exercise group, and 26-28m/min(70-85%VO2max) in high exercise group. Rats in the exercise groups were subjected to a 8 week-treadmill exercise, 0°slope, 60 min/day, 5 days/week. Blood pressure examined by non-invasive methods, endothelial microstructure observed by electric microscope, tension test to isolated micro artery measured by DMT, protein determined by western blotting and detection for enzyme activity illustrate how endothelial function exert in mesentery artery as peripheral resistance. To discuss an oxidative stress mechanisms that effect endothelial function in hypertension at different intensity exercise. Result:(1) Blood pressure in SHR-M was much higher than in SHR-C which was higher than SHR-M.(2) To rule out microvascular individual differences, KCL(60mM)stimulated vessel, which generate maximum contract as 100%KMAX.Then the vessel was contracted by NE. %KMAX as a mark to evaluate the vascular contract response. WKY-M(154.09±2.31%KMAX)was strikingly lower in comparison with WKY-H(198.17±9.07%KMAX)(P<0.05); Compared with SHR-C(190.64±9.14% KMAX), SHR-M(155.83±5.13% KMAX) was much lower.(3) When the peak value contracted by NE as 100% response,endothelium dependent dilation(%NE) induced by ACh was used to evaluate endothelial function. SHR-C(87.23±4.79%NE) was strikingly lower in comparison with WKY-C(97.94±1.20%NE); SHR-M ameliorated endothelium dependent dilation dysfunction induced by hypertension; However, dilation was apparently decreased in SHR-H compared to SHR-C(P<0.05).(4)The most common indicators of Oxidation products and antioxidant enzymes are MDA, GSH-Px, SOD. MDA in SHR-C(10.89±1.19 nmol/ml) had a ascend trend but no apparent difference in comparison with WKY-C. GSH-Px in SHR-C(1348.09±42.46 U) were lower in comparison with WKY-C(1562.55±68.82 U); MDA in SHR-H(21.03±3.06nmol/ml) were higher than compared to SHR-C(10.89±1.19nmol/ml)(P<0.05), GSH-Px in SHR-H were higher compared to SHR-C(P<0.05); MDA in SHR-M(10.65±2.00 nmol/ml) had no apparent difference compared to SHR-C, but GSH-Px were higher(P<0.05)(5)Expression of eNOS protein was significantly increased in high blood pressure groups under exercise. Inhibitor of eNOS was added to bed for calculating NO-dependent relaxation(%), which had significant difference between SHR-C(40.13±1.07%) and SHR-M(46.83±0.79%). SHR-M was significantly higher in comparison with SHR-C. However, SHR-H was much lower than SHR-C. Compared with different intensity exercise that probably exerted the consequences,SHR-M had higher NO-dependent relaxation(%) than SHR-H(13.38±0.09%). NO-dependent relaxation(%) is to evaluate NO bioavailability. The contradiction between expression of eNOS protein and NO bioavailability, increased or constant expression of protein with decreased NO bioavailability, are treated as “eNOS uncoupling”. Conclusion: Moderate exercise can reduce the SBP, while high exercise have an opposite effect. High blood pressure can induce the disorder of endothelium dependent dilation. Moderate exercise can improve it, while high exercise break it. |
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