BACKGROUND: Skeletal muscle dysfunction contributes to exercise limitation in COPD. The role of the nitric oxide synthase (NOS) system in muscle dysfunction is ill defined. Reduced levels of endothelial NOS (eNOS) and elevated levels of inducible NOS (iNOS) in the skeletal muscle of COPD patients have been recently reported. We hypothesized that resistance exercise training (R) and/or testosterone supplementation (T) would alter the transcription and expression of the NOS isoenzymes in COPD skeletal muscle. METHODS: Vastus lateralis biopsies were obtained before and after a 10-week intervention in 40 men with severe COPD (age 67.7 +/- 8.3, FEV1 41.4 +/- 12.6% predicted): placebo plus no training (P) (n = 11), placebo plus resistance training (PR) (n = 8), testosterone plus no training (T) (n = 11) and testosterone plus resistance training (TR) (n = 10) groups. eNOS, nNOS and iNOS mRNA and protein levels were measured in each sample. mRNA and protein levels were measured using real-time PCR and enzyme-linked immunosorbant assay, respectively. RESULTS: eNOS mRNA increased in the TR group compared to P and T groups (p < 0.001). eNOS protein was increased in TR and T groups after intervention (p < 0.05) but not in the PR group. nNOS protein increased in the PR, T, and TR groups (p < 0.05). iNOS protein decreased only in the TR group (p = 0.01). CONCLUSION: Resistance training and testosterone supplementation increased eNOS and nNOS proteins and decreased iNOS protein in the skeletal muscles of men with COPD. These changes in NO system might explain some of the favorable effects of these therapies.

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