| Summary: | 碩士 === 國立臺灣大學 === 物理治療學研究所 === 102 === Background: Radiotherapy (RT) had shown to induce acute diaphragm contractile dysfunction. Inspiratory muscle training (IMT) have proven to be effective in enhancing contractile function of the muscle; however, whether IMT prior to RT could ameliorate RT-related contractile dysfunction remains to be determined. Purposes: The purposes of this study were to investigate: 1) the effect of 1-week resistive breathing training on contractile function, antioxidant capacity and oxidative injury of the diaphragm; and 2) the effect of this training on RT-induced diaphragm contractile dysfunction and exploring the potential underlying mechanism in animal model. Methods: This study included two phases. In phase I, Sprague-Dawley (SD) rats were randomized into training (TG, n=7) or sham training (SG, n=6) group. TG received resistive breathing training using tracheal banding method for 1-week and SG received sham operation. Upon the completion of training, rats in both groups were sacrificed and the diaphragms were removed en bloc for contractile function assessment, antioxidant capacity and oxidative injury analysis. Antioxidant capacity analysis included total SOD activity, CuZnSOD and MnSOD mRNA expression. Oxidative injury was analyzed using protein carbonyl and 8-OHdG. In phase II, SD rats were randomized into training then RT (TR, n=6) or sham training then RT (SR, n=6) group. Training method was identical to that of phase I. After the completion of training, rats in both groups received one-shot 5 Gy RT to the diaphragm region. Twenty-four hours following RT, all rats were sacrificed and the diaphragms were removed for all the analyses as described in phase I. Generalized Estimated Equation and Generalized Linear Model were used to detect differences of variables between and within groups when suitable. Significant α level was set at 0.05. Results: Tracheal banding provided an average of 1.6 times increases in airway resistance. After 1-week of training, contractility (p<0.05), total SOD activity (p=0.004), and MnSOD mRNA expression (p=0.03) of the diaphragm were significantly higher in TG than those of SG. However, protein carbonyl level of the diaphragm were also increased after training (p<0.001). In phase II, contractility of the diaphragm were significantly higher (p<0.05), while fatigue index (p=0.002) and protein carbonyl level (p<0.001) were lower in TR than those of SR. Compared to SR, relative force-frequency curve showed significant downward shift between 30-50 Hz in TR. mRNA expression of CuZnSOD and MnSOD were significant higher in TR than those of SR (both p<0.05). Conclusions: This study showed that 1-week resistive breathing training could enhance diaphragm contractile function and thus reducing RT-induced its dysfunction through training related upregulation of antioxidant capacity of the diaphragm.
|
|---|
