Oxidative stress and peripheral skeletal muscle dysfunction in rats with emphysema

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 forthis functional impairment is uncertain,oxidative stress may play a role.The purpose of this study was to investigatewhether local oxidative stress is associated with the reduced peripheral skeletal muscle performance in rats withemphysema.Methods In situ mechanical properties of gastrocnemius were measured in Sprague-Dawley rats 5 months afterintratracheal instillation of either elastase (EMP,n=10) or normal saline (CON,n=10).Lipofuscin inclusions,myocyteapoptosis 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±0.4 vs.1.7±0.4,P<0.01).The activities of antioxidant enzymes were significantly increased in muscle homogenatesof EMP as compared to CON.No significant differences were found in myocyte apoptosis between EMP and CON(1.2±0.9 vs.1.0±0.8,P >0.05).EMP decreased the fatigue endurance of gastrocnemius muscle (half-time to fatiguerecovery:(150.0±55.4) seconds vs.(55.2±29.3) seconds,P <0.01) and had no effect on maximal tetanic force((467.4±36.6) g vs.(493.2±30.5) g,P>0.05).A significantly positive correlation was found between the level of lipofuscininclusions 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 ratswith EMP.