Abstract
PURPOSE The purpose of this study was to determine the effects of experimental chronic heart failure (CHF) on maximal sarcoplasmic reticulum Ca2+-ATPase activity (Vmax) and Hill co-efficient (nH) in soleus (SOL), red gastrocnemius (RG) and white gastrocnemius (WG) and left ventricle (LV). METHODS Experimental CHF following ligation of the left main coronary artery in adult rats was confirmed by elevations (p < 0.05) in left-ventricle to body wt ratios (0.168±0.04 vs 0.186±0.07 g/g.100) in CHF compared to controls (CON). RESULTS Comparisons between CHF (n = 8) and CON (n = 8) indicated reduced (p < 0.05) Vmax (μmol.g protein−1·min−1) in SOL (197±22 vs 152±20), RG (399±8.2 vs 314±25) and WG (584±47 vs 449±59) in CHF. The nH was not different between CHF and CON for any of the muscles examined. The lower Vmax was accompanied by increases (p < 0.05) in SERCA 2 (% standard) in RG (38.7±10 vs 56.1±7.6) and WG (19.4±3.0 vs 27.0±2.2) only. No changes were observed in SERCA 1, as measured by Western blotting techniques. Reductions in Vmax were observed for LV (207±22 vs 162±14) in the absence of change in SERCA 2. CONCLUSION These results suggest that altered protein levels cannot explain the reduced Vmax observed in CHF. The results also suggest that defects in Ca2+-cycling may be involved in weakness and fatigue in CHF. Supported by Heart and Stroke Foundation (Ontario)
Published Version
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