Green H, Roy B, Grant S, Otto C, Pipe A, McKenzie D, Johnson M
Department of Kinesiology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Am J Physiol Regul Integr Comp Physiol. 2000 Nov;279(5):R1872-9. doi: 10.1152/ajpregu.2000.279.5.R1872.
Chronic exposure to high altitude is known to result in changes in the mechanisms regulating O(2) delivery to the contracting muscle. However, the effects of acclimatization on metabolism in the contracting muscle cell remain unclear. In this study, we have investigated the hypothesis that acclimatization would result in a closer coupling between ATP utilization and ATP production and that the improved energy state would be accompanied by a reorganization of the metabolic pathways consisting of an increased oxidative and decreased glycolytic potential. Five men, mean age of 28 +/- 2 (SE) yr, performed a standardized, two-stage submaximal cycling task in normoxia for 20 min at each of 59 and 74% peak O(2) consumption before and 3-4 days after returning from a 21-day expedition to Mount Denali (6,194 m). Acclimatization was without effect in altering the resting values of the adenine nucleotides (ATP, ADP, AMP), inosine monophosphate (IMP), or phosphocreatine (PCr) in the vastus lateralis. During exercise (40 min) after acclimatization compared with preacclimatization, PCr was not as depressed (33.2 +/- 7.1 vs. 40.6 +/- 5.4 mmol/kg dry wt) and IMP (0.289 +/- 0.11 vs. 0. 131 +/- 0.03 mmol/kg dry wt) and lactate (26.1 +/- 6.2 vs. 18.6 +/- 8.8 mmol/kg dry wt) in contracting muscle were not as elevated (P < 0.05). Although no effect of acclimatization was observed for the maximal activity (mol. kg protein(-1). h(-1)) of citrate synthase (4. 76 +/- 0.44 vs. 4.94 +/- 0.45), lactate dehydrogenase was increased by 13% (36.5 +/- 2.6 vs. 41.2 +/- 3.1, P < 0.05). It is concluded that acclimatization results in an improved energy state in the contracting muscle when tested under normoxic conditions; however, these effects are not associated with a higher oxidative potential or a lower glycolytic potential as hypothesized.
已知长期暴露于高海拔环境会导致调节氧气输送至收缩肌肉的机制发生变化。然而，适应过程对收缩肌肉细胞代谢的影响仍不明确。在本研究中，我们探讨了以下假设：适应过程会使ATP利用与ATP生成之间的耦合更紧密，且能量状态的改善将伴随着代谢途径的重组，即氧化能力增强和糖酵解能力降低。五名平均年龄为28±2（标准误）岁的男性，在常氧条件下进行了一项标准化的两阶段次最大强度骑行任务，在前往德纳里峰（6,194米）进行21天探险之前以及返回后3 - 4天，分别在59%和74%的峰值耗氧量下各骑行20分钟。适应过程对股外侧肌中腺嘌呤核苷酸（ATP、ADP、AMP）、肌苷单磷酸（IMP）或磷酸肌酸（PCr）的静息值没有影响。与适应前相比，适应后运动（40分钟）期间，PCr的降低程度较小（33.2±7.1对40.6±5.4 mmol/kg干重），收缩肌肉中的IMP（0.289±0.11对0.131±0.03 mmol/kg干重）和乳酸（26.1±6.2对18.6±8.8 mmol/kg干重）升高幅度也较小（P<0.05）。尽管未观察到适应对柠檬酸合酶的最大活性（mol·kg蛋白质⁻¹·h⁻¹）有影响（4.76±0.44对4.94±0.45），但乳酸脱氢酶增加了13%（36.5±2.6对41.2±3.1，P<0.05）。得出的结论是，在常氧条件下进行测试时，适应过程会使收缩肌肉的能量状态得到改善；然而，这些影响与假设的更高氧化能力或更低糖酵解能力无关。
