Exercise training attenuates aging-associated increases in collagen and collagen crosslinking of the left but not the right ventricle in the rat

Abstract.

The purpose of this study was to compare the independent and interactive effects of age and exercise training on selected parameters of the right ventricle (RV), left ventricular septum (LVS) and left ventricular free-wall (LVFW) extracellular matrix. Specifically, we evaluated collagen and collagen crosslinking (hydroxylysylpyridinoline, HP) concentrations in the myocardial extracellular matrix in young adult, Y (5.5 months) and old, O (25.5 months) male Fischer 344 rats. Rats were assigned to either a sedentary control (YC, OC) or an exercise training group (YT, OT). Rats were trained for 45 min/day, 5 days/week, for 10 weeks at ≅70% of maximal oxygen consumption. Following the training regimen, rats were sacrificed and their hearts were dissected into the RV, LVS and LVFW. Training resulted in a significant hypertrophy of the left ventricle (LV) but not RV relative to body weight. In young rats, collagen concentration was significantly higher (P<0.01) in RV compared to LVS, but not LVFW. With aging, collagen concentration increased significantly (P<0.05) in both ventricles, but more so in LV than RV so that differences in percent collagen observed between chambers in both YC and YT rats no longer existed in OC and OT animals. This aging effect was attenuated by training in the LVS but not the LVFW, so that collagen concentration, while higher in this region of the LV in OT compared to YT rats, was also lower than that seen in the LVS of OC rats. HP crosslink concentration in the LVS and LVFW, but not the RV of OC rats was significantly elevated above corresponding values seen in YC rats (P<0.05 or greater). In YT rats, training had no effect on HP crosslinking concentration in any of the three regions of the heart. However, in OT rats, training completely prevented the age-associated increase in crosslinking seen in both the LVS and LVFW of OC animals. These findings illustrate the different responses of the RV, LVS and LVFW extracellular matrix components, collagen and HP crosslinking, to both aging and training in the rodent.