OXIDATIVE STRESS-INDUCED BY INTERMITTENT EXPOSURE AT A SIMULATED ALTITUDE OF 4000-M DECREASES MITOCHONDRIAL SUPEROXIDE-DISMUTASE CONTENT INSOLEUS MUSCLE OF RATS

The effects were examined of 6-month intermittent hypobaric (4000 m) e xposure on the antioxidant enzyme systems in soleus and tibialis muscl es of rats. At the end of the 6-month experimental exposure, the six r ats in both the exposed group and the control group were sacrificed. I mmunoreactive mitochondrial superoxide dismutase (Mn-SOD) contents wer e measured as well as the activities of antioxidant enzymes [Mn-SOD, c ytosolic SOD (Cu,Zn-SOD), catalase (CAT), and glutathione peroxidase ( GPX)]. Thiobarbituric acid-reactive substances (TBARS) were also deter mined as an indicator of lipid peroxidation. The high altitude exposur e resulted in a marked increase in TBARS content in soleus muscle, sug gesting increased levels of oxygen free radicals. Conversely, signific ant decreases in both Mn-SOD content and activity in soleus muscle wer e noted affer exposure. Such trends were not noticed in tibialis muscl e. On the other hand, no significant changes in Cu,Zn-SOD, CAT, or GPX were observed in either muscle. These results suggested that the incr eases in lipid peroxidation were most probably a result of decreased M n-SOD function which was more depressed in oxidative than in glycolyti c muscle.