We evaluated the influence of aerobic training on cardiac remodeling in untreated spontaneously hypertensive rats (SHR). Four experimental groups were used: sedentary (W-SED, n=27) and trained (WEX, n=31) normotensive Wistar rats, and sedentary (SHR-SED, n=27) and exercised (SHR-EX, n=32) hypertensive rats. At 13 months old, trained groups underwent treadmill exercise five days a week for four months. Statistical analysis: ANOVA or Kruskal-Wallis. Exercised groups had higher physical capacity. Hypertensive groups presented left ventricular (LV) concentric hypertrophy with impaired function. Left atrium diameter, LV posterior wall thickness and relative thickness, and isovolumetric relaxation time were lower in SHR-EX than SHR-SED. Interstitial collagen fraction and Type I-Type III collagen ratio were higher in SHR-SED than W-SED. In SHR-EX these parameters had intermediate values between W-EX and SHRSED with no differences between either group. Myocardial matrix metalloproteinase-2 activity, evaluated by zymography, was higher in SHR-SED than W-SED and SHR-EX. TIMP-2 was higher in hypertensive than normotensive groups. In conclusion, low intensity aerobic exercise reduces left atrium dimension and LV posterior wall thickness, and improves functional capacity, diastolic function, and metalloproteinase-2 activity in adult SHR.
