Background: Peripheral skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD) may be due to the disease per se or as a result of concomitant confounding factors. Although the mechanistic basis for this functional impairment is uncertain, oxidative stress may play a role. The purpose of this study was to investigate whether local oxidative stress is associated with the reduced peripheral skeletal muscle performance in rats with emphysema.
Methods: In situ mechanical properties of gastrocnemius were measured in Sprague-Dawley rats 5 months after intratracheal instillation of either elastase (EMP, n = 10) or normal saline (CON, n = 10). Lipofuscin inclusions, myocyte apoptosis and antioxidant enzyme activities were examined in the gastrocnemius muscle.
Results: Lipofuscin inclusions were significantly higher in the gastrocnemius muscle of EMP compared with CON (3.2 + or - 0.4 vs. 1.7 + or - 0.4, P < 0.01). The activities of antioxidant enzymes were significantly increased in muscle homogenates of EMP as compared to CON. No significant differences were found in myocyte apoptosis between EMP and CON (1.2 + or - 0.9 vs. 1.0 + or - 0.8, P > 0.05). EMP decreased the fatigue endurance of gastrocnemius muscle (half-time to fatigue recovery: (150.0 + or - 55.4) seconds vs. (55.2 + or - 29.3) seconds, P < 0.01) and had no effect on maximal tetanic force ((467.4 + or - 36.6) g vs. (493.2 + or - 30.5) g, P > 0.05). A significantly positive correlation was found between the level of lipofuscin inclusions and the half-time to fatigue recovery of gastrocnemius muscle in EMP (r = 0.664, P < 0.05).
Conclusion: Local oxidative stress may have important functional consequences for peripheral skeletal muscle in rats with EMP.