Green H J, Grant S M, Phillips S M, Enns D L, Tarnopolsky M A, Sutton J R
Department of Kinesiology, University of Waterloo, ON, Canada.
Can J Physiol Pharmacol. 1997 Dec;75(12):1280-6.
To examine the effects of a dilutional mediated decrease in arterial O2 content on muscle metabolic and substrate behaviour during exercise, plasma volume was acutely expanded by either 14% (LOW) or 21% (HIGH) using a 6% dextran solution dissolved in saline (Macrodex) and compared with a control (CON) condition. The exercise protocol, performed by eight untrained males (VO2max = 45.2 +/- 2.2 mL.kg-1.min-1, X +/- SE) and with the conditions randomized, was conducted for 120 min at 46 +/- 4% VO2max. The content of inosine monophosphate determined on muscle tissue extracted from the vastus lateralis increased (p < 0.05) by 120 min of exercise (0.119 +/- 0.02 vs 0.493 +/- 0.19 mmol/kg dry weight) in CON. No effect of either LOW or HIGH expansion of plasma volume was found. Similarly, phosphocreatine content (mmol/kg dry weight), although reduced (p < 0.05) with exercise, was not different between the conditions at either 3 min (61.9 +/- 3.5, 66.2 +/- 3.5, 64.3 +/- 2.1) or 120 min (52.5 +/- 6.3, 53.8 +/- 5.8, 59.4 +/- 5.5) of exercise. In contrast, both pyruvate and lactate were reduced (p < 0.05) by 3 min of exercise in both LOW and HIGH compared with CON. The reduction in these metabolites with plasma volume expansion was not accompanied by an alteration in glycogen depletion rates. Steady-state VO2 was unaffected by acute hypervolemia. These results suggest that moderate exercise following an approximate 10% reduction in arterial O2 content can be performed without increasing the imbalance between ATP production and utilization rates. Since high energy phosphate transfer and glycolysis appeared not to be increased, mitochondrial respiration was apparently preserved by mechanisms as yet undetermined.
为研究运动期间稀释介导的动脉血氧含量降低对肌肉代谢和底物行为的影响，使用溶解于生理盐水中的6%右旋糖酐溶液（Macrodex）使血浆量急性增加14%（低剂量组）或21%（高剂量组），并与对照组（CON）进行比较。由8名未经训练的男性（最大摄氧量 = 45.2 ± 2.2 mL·kg⁻¹·min⁻¹，X ± SE）执行运动方案，且条件随机化，在46 ± 4%最大摄氧量下进行120分钟。在CON组中，运动120分钟后，从股外侧肌提取的肌肉组织中测定的肌苷单磷酸含量增加（p < 0.05）（0.119 ± 0.02 vs 0.493 ± 0.19 mmol/kg干重）。未发现血浆量低剂量或高剂量增加有任何影响。同样，磷酸肌酸含量（mmol/kg干重）虽然在运动时降低（p < 0.05），但在运动3分钟（61.9 ± 3.5、66.2 ± 3.5、64.3 ± 2.1）或120分钟（52.5 ± 6.3、53.8 ± 5.8、59.4 ± 5.5）时，各条件之间并无差异。相比之下，与CON组相比，低剂量组和高剂量组在运动3分钟时丙酮酸和乳酸均降低（p < 0.05）。这些代谢物随血浆量增加的减少并未伴随糖原消耗率的改变。稳态最大摄氧量不受急性血容量过多的影响。这些结果表明，在动脉血氧含量约降低10%后进行适度运动，不会增加ATP产生与利用率之间的不平衡。由于高能磷酸转移和糖酵解似乎未增加，线粒体呼吸显然通过尚未确定的机制得以保留。
