TRICARBOXYLIC-ACID CYCLE INTERMEDIATES IN HUMAN MUSCLE DURING PROLONGED EXERCISE
TRICARBOXYLIC-ACID CYCLE INTERMEDIATES IN HUMAN MUSCLE DURING PROLONGED EXERCISE
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DOI：
10.1152/ajpcell.1990.259.5.c834
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发表时间：
1990-11-01
影响因子：
--
通讯作者：
BROBERG, S
中科院分区：
文献类型：
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作者：
SAHLIN, K;KATZ, A;BROBERG, S
7名受试者骑自行车疲劳[75 .+-. 5（SE）min]，其工作负荷对应于其最大摄氧量的约75%。在休息和运动期间从股四头肌肌肉中取出活检。肌肉糖原从运动前的445 ± 0.001水平下降。33 mmol葡糖基单位/kg干重至50 ±. 14疲劳测得的三羧酸循环中间体（TCAI =苹果酸盐+柠檬酸盐+富马酸盐+草酰乙酸盐）的总和为0.49。0.05在静止时，mmol/kg干重增加到4.41 . ±. 0.23运动5 min后，继续下降至3.33 ± 0.01。0.29和2.83 ±。0.27运动40 min后和疲劳状态下的血浆蛋白水平分别为1.0mmol/kg干重（P < 0.05 vs.5 min）。疲劳点的特征在于AMP的脱氨作用增强（通过IMP的增加来判断）和乳酸、丙酮酸和丙氨酸的含量降低（与5分钟的运动相比）。相反，乙酰肉碱（反映乙酰单位的可用性）增加三倍，在运动开始时，并保持在这个水平，直到疲劳。它的结论是，长期运动疲劳在中等工作负荷的结果，糖原耗竭，能量不足（增加AMP脱氨），降低水平的三碳化合物和TCAI（与运动的初始阶段相比），但在维持水平的乙酰单位。目前的数据表明，碳水化合物消耗可能会通过降低TCAI水平而损害有氧能量的产生。
Seven subjects cycled to fatigue [75 .+-. 5 (SE) min] at a work load corresponding to .apprx.75% of their maximal oxygen uptake. Biopsies were taken from the quadriceps femoris muscle at rest and during exercise. Muscle glycogen decreased from a preexercise level of 445 .+-. 33 mmol glucosyl units/kg dry wt to 50 .+-. 14 at fatigue. The sum of the measured tricarboxylic acid cycle intermediates (TCAI = malate + citrate + fumarate + oxaloacetate) was 0.49 .+-. 0.05 mmol/kg dry wt at rest, increased to 4.41 .+-. 0.23 after 5 min of exercise, and then decreased continuously to 3.33 .+-. 0.29 and to 2.83 .+-. 0.27 mmol/kg dry wt after 40 min of exercise and at fatigue (P < 0.05 vs. 5 min), respectively. The point of fatigue was characterized by an enhanced deamination of AMP (judged by increase in IMP) and reduced contents (vs. 5 min of exercise) of lactate, pyruvate, and alanine. In contrast, acetylcarnitine (reflects the availability of acetylunits) increased threefold at the onset of exercise and was maintained approximately at this level until fatigue. It is concluded that prolonged exercise to fatigue at moderate work loads results in glycogen depletion, energy deficiency (increased AMP deamination), reduced levels of three-carbon compounds and TCAI (compared with the initial phase of exercise) but in maintained levels of acetylunits. The present data indicate that carbohydrate depletion may impair aerobic energy production by reducing the level of TCAI.