Collagen gene expression in rat left ventricle: interactive effect of age and exercise training

Whether or not exercise training of sufficient intensity and duration to pr oduce left ventricle (LV) hypertrophy also regulates deposition of intersti tial collagen and cross-linking at the pretranslational level is unknown. T herefore, the effects of exercise training on gene expression for the two p rincipal fibrillar collagens in LV, types I and III, were assessed in young adult (5 mo), middle-aged (15 mo), and old (26 mo) rats. We also evaluated the potential interaction of changes in mRNA for these procollagens with a lterations in LV extracellular matrix characteristics by simultaneously mea suring collagen concentration (hydroxyproline) and extent of mature collage n cross-linking hydroxylysylpyridinoline, HP). Ten weeks of treadmill runni ng resulted in LV hypertrophy and an increased maximal oxygen uptake in all three age groups of trained rats compared with sedentary controls. Percent collagen in rat LV almost doubled (P < 0.0001) from 5 to 26 mo of age, an increase unaffected by exercise training. With aging, a significant decline in expression of mRNAs for both collagen type I (P < 0.005) and type III ( P < 0.001) was observed in LV free wall (LVF) but not septum (LVS). Trainin g prevented this decline in LVF mRNAs for the two principal fibrillar colla gens in middle-aged rats whereas it attenuated the decline in senescent ani mals. KP concentration increased significantly with aging in both LVF (P < 0.005) and LVS (P < 0.01). Training modulated this effect, but again only i n LVF, so that HP was significantly lower (P < 0.05) in this region of the LV in old trained rats compared with sedentary counterparts. We conclude th at exercise training modulates the effects of aging on collagen gene mRNAs and HP cross-linking regionally within the LV.