MYOGLOBIN O-2 DESATURATION DURING EXERCISE - EVIDENCE OF LIMITED O-2 TRANSPORT
MYOGLOBIN O-2 DESATURATION DURING EXERCISE - EVIDENCE OF LIMITED O-2 TRANSPORT
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DOI：
10.1172/jci118237
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发表时间：
1995-10-01
影响因子：
15.9
通讯作者：
WAGNER, PD
中科院分区：
文献类型：
--
作者：
RICHARDSON, RS;NOYSZEWSKI, EA;WAGNER, PD
在最大限度地锻炼肌肉时，细胞氧压（PO2）接近于零，这一假设对于血液和线粒体之间的O-2运输具有有限的传导性这一假设至关重要，该传导性决定了O-2的最大消耗。在6名训练有素的男性呼吸室内空气（常氧，N）和12% O-2（低氧，H）的情况下，将孤立的人体四头肌锻炼、直接测量动脉、股静脉PO2和H-1核磁共振波谱检测肌红蛋白去饱和的独特组合，使这一假设得到了验证。在运动开始的20秒内，即使在最大O-2消耗的50%时，肌红蛋白的部分去饱和也很明显，在H下明显大于N，然后在整个增量运动方案中平均保持在51+/-3% (N)和60+/-3% (H)，直到最大工作速率。假设50%的肌红蛋白结合位点与O-2结合的肌红蛋白PO2为3.2 mmHg，则肌红蛋白相关PO2平均为3.1+/- 0.3(N)和2.1+/- 0.2 mmHg (H)。在最大运动时，测量动脉PO2 （115+/-4 [N]和46+/-1 mmHg [H]）和股静脉PO2 (22+/-1.6 [N]和17+/-1.3 mmHg [H])，计算出平均毛细血管PO2值为38+2 (N)和30+/-2 mmHg (H)。因此，这是第一次，在完整的正常人体肌肉中，血液和细胞内组织之间的PO2存在巨大差异，并且在很宽的运动强度范围内被发现，这些数据与从红细胞到肌膜的1-5 μ m路径长度上的O-2扩散限制一致，这在决定正常人体最大肌肉O-2摄取中起作用。
The assumption that cellular oxygen pressure (PO2) is close to zero in maximally exercising muscle is essential for the hypothesis that O-2 transport between blood and mitochondria has a finite conductance that determines maximum O-2 consumption. The unique combination of isolated human quadriceps exercise, direct measures of arterial, femoral venous PO2, and H-1 nuclear magnetic resonance spectroscopy to detect myoglobin desaturation enabled this assumption to be tested in six trained men while breathing room air (normoxic, N) and 12% O-2 (hypoxic, H). Within 20 s of exercise onset partial myoglobin desaturation was evident even at 50% of masimum O-2 consumption, was significantly greater in H than N, and was then constant at an average of 51+/-3% (N) and 60+/-3% (H) throughout the incremental exercise protocol to maximum work rate. Assuming a myoglobin PO2 where 50% of myoglobin binding sites are bound with O-2 of 3.2 mmHg, myoglobin-associated PO2 averaged 3.1+/-.3 (N) and 2.1+/-.2 mmHg (H). At maximal exercise, measurements of arterial PO2 (115+/-4 [N] and 46+/-1 mmHg [H]) and femoral venous PO2 (22+/-1.6 [N] and 17+/-1.3 mmHg [H]) resulted in calculated mean capillary PO2 values of 38+2 (N) and 30+/-2 mmHg (H). Thus, for the first time, large differences in PO2 between blood and intracellular tissue have been demonstrated in intact normal human muscle and are found over a wide range of exercise intensities, These data are consistent with an O-2 diffusion limitation across the 1-5-mu m path-length from red cell to the sarcolemma that plays a role in determining maximal muscle O-2 uptake in normal humans.