Effects of endurance training under hyperoxia on carbohydrate and fat metabolism in rats / 体力科学

ABSTRACT

The effects of 6 weeks (5 days/week) of endurance training under hyperoxia (60% O<SUB>2</SUB> plus 40% N<SUB>2</SUB>) on carbohydrate and fat metabolism were studied in 42 male rats. The rats were divided into four groups ; normoxia control (NC, n=8), hyperoxia control (HC, n=9), normoxia training (NT, n=12), and hyperoxia training (HT, n=13) . NT and HT groups were made to run on a treadmill in a metabolic chamber at a speed of 20 m/min for 30 min. The metabolic chamber was perfused with hyperoxic gas. VCO<SUB>2</SUB> values at rest (HC) and during exercise (HT) under hyperoxia were significantly lower (p<0.01) than VCO<SUB>2</SUB> values at rest (NC) and during exercise (NT) under normoxia, respectively. These results appear to indicate that a decreased respiratory exchange ratio was induced by hyperoxia. The results showed that at 15 min after the last training there were no differences between NT and HT in the glycogen or triglyceride content of the liver, heart, m, gastrocnemius, and m. soleus. However, blood glucose at 15 min in NT (109±13 mg/d<I>l</I>) was significantly lower (p<0.05) than the corresponding value at 15 min in HT (133±11 mg/d<I>l</I>) and at 48 h after the last training in NT (149±7 mg/d<I>l</I>) . The glycogen content of the liver in HC (36.4±2.6 mg/g wet wt) was significantly higher (p<0.05) than the corresponding value in NC (26.1±1.9 mg/g wet wt) . In the HT group, the triglyceride content of the liver at 48 h was lower (p<0.01) than the corresponding value at 15 min. However, the triglyceride content of the heart at 48 h in HT was significantly higher (p<0.05) than the value at 15 min. Basal lipolysis in HC was significantly higher than the corresponding values in NC, NT and HT, but there were no differences among the groups in norepinephrine-induced lipolysis. These results indicate that endurance training under hyperoxia might alter the content of tissue glycogen and triglyceride as a result of decreased carbohydrate consumption and increased fat utilization during fasting and/or exercise.