Putman C T, Jones N L, Hultman E, Hollidge-Horvat M G, Bonen A, McConachie D R, Heigenhauser G J
Department of Medicine, McMaster University Medical Centre, Hamilton, Ontario L8N 3Z5, Canada.
Am J Physiol. 1998 Jul;275(1):E132-9. doi: 10.1152/ajpendo.1998.275.1.E132.
Muscle metabolism, including the role of pyruvate dehydrogenase (PDH) in muscle lactate (Lac-) production, was examined during incremental exercise before and after 7 days of submaximal training on a cycle ergometer [2 h daily at 60% peak O2 uptake (VO2 max)]. Subjects were studied at rest and during continuous steady-state cycling at three stages (15 min each): 30, 65, and 75% of the pretraining VO2 max. Blood was sampled from brachial artery and femoral vein, and leg blood flow was measured by thermodilution. Biopsies of the vastus lateralis were obtained at rest and during steady-state exercise at the end of each stage. VO2 max, leg O2 uptake, and the maximum activities of citrate synthase and PDH were not altered by training; muscle glycogen concentration was higher. During rest and cycling at 30% VO2 max, muscle Lac- concentration ([Lac-]) and leg efflux were similar. At 65% VO2 max, muscle [Lac-] was lower (11.9 +/- 3.2 vs. 20.0 +/- 5.8 mmol/kg dry wt) and Lac- efflux was less [-0.22 +/- 0.24 (one leg) vs. 1.42 +/- 0.33 mmol/min] after training. Similarly, at 75% VO2 max, lower muscle [Lac-] (17.2 +/- 4.4 vs. 45.2 +/- 6.6 mmol/kg dry wt) accompanied less release (0.41 +/- 0.53 vs. 1.32 +/- 0.65 mmol/min) after training. PDH in its active form (PDHa) was not different between conditions. Calculated pyruvate production at 75% VO2 max fell by 33%, pyruvate reduction to lactate fell by 59%, and pyruvate oxidation fell by 24% compared with before training. Muscle contents of coenzyme A and phosphocreatine were higher during exercise after training. Lower muscle lactate production after training resulted from improved matching of glycolytic and PDHa fluxes, independently of changes in muscle O2 consumption, and was associated with greater phosphorylation potential.
在递增运动期间，研究了肌肉代谢，包括丙酮酸脱氢酶（PDH）在肌肉乳酸（Lac-）生成中的作用，研究对象是在周期测力计上进行7天次最大训练（每天2小时，运动强度为峰值摄氧量（VO2 max）的60%）前后的情况。在静息状态以及三个阶段（每个阶段15分钟）的持续稳态骑行过程中对受试者进行研究，这三个阶段的运动强度分别为训练前VO2 max的30%、65%和75%。从肱动脉和股静脉采集血液样本，并通过热稀释法测量腿部血流量。在静息状态以及每个阶段结束时的稳态运动期间采集股外侧肌活检样本。VO2 max、腿部摄氧量以及柠檬酸合酶和PDH的最大活性并未因训练而改变；肌肉糖原浓度有所升高。在静息状态以及运动强度为VO2 max的30%时进行骑行，肌肉Lac-浓度（[Lac-]）和腿部流出量相似。在运动强度为VO2 max的65%时，训练后肌肉[Lac-]较低（11.9±3.2与20.0±5.8 mmol/kg干重），Lac-流出量较少[-0.22±0.24（单腿）与1.42±0.33 mmol/min]。同样，在运动强度为VO2 max的75%时，训练后肌肉[Lac-]较低（17.2±4.4与45.2±6.6 mmol/kg干重），伴随的释放量较少（0.41±0.53与1.32±0.65 mmol/min）。活性形式的PDH（PDHa）在不同条件下并无差异。与训练前相比，在运动强度为VO2 max的75%时，计算得出的丙酮酸生成量下降了33%，丙酮酸还原为乳酸的量下降了59%，丙酮酸氧化量下降了24%。训练后运动期间肌肉中辅酶A和磷酸肌酸的含量较高。训练后肌肉乳酸生成量降低是由于糖酵解和PDHa通量的匹配改善，这与肌肉耗氧量的变化无关，并且与更高的磷酸化潜能相关。
