Haseler L J, Richardson R S, Videen J S, Hogan M C
Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA.
J Appl Physiol (1985). 1998 Oct;85(4):1457-63. doi: 10.1152/jappl.1998.85.4.1457.
There is evidence that the concentration of the high-energy phosphate metabolites may be altered during steady-state submaximal exercise by the breathing of different fractions of inspired O2 (FIO2). Whereas it has been suggested that these changes may be the result of differences in time taken to achieve steady-state O2 uptake (V(O2)) at different FIO2 values, we postulated that they are due to a direct effect of O2 tension. We used 31P-magnetic resonance spectroscopy during constant-load, steady-state submaximal exercise to determine 1) whether changes in high-energy phosphates do occur at the same V(O2) with varied FIO2 and 2) that these changes are not due to differences in V(O2) onset kinetics. Six male subjects performed steady-state submaximal plantar flexion exercise [7.2 +/- 0.6 (SE) W] for 10 min while lying supine in a 1.5-T clinical scanner. Magnetic resonance spectroscopy data were collected continuously for 2 min before exercise, 10 min during exercise, and 6 min during recovery. Subjects performed three different exercise bouts at constant load with the FIO2 switched after 5 min of the 10-min exercise bout. The three exercise treatments were 1) FIO2 of 0.1 switched to 0.21, 2) FIO2 of 0.1 switched to 1.00, and 3) FIO2 of 1.00 switched to 0.1. For all three treatments, the FIO2 switch significantly (P </= 0.05) altered phosphocreatine: 1) 55.5 +/- 4.8 to 67.8 +/- 4.9% (%rest); 2) 59.0 +/- 4.3 to 72.3 +/- 5.1%; and 3) 72.6 +/- 3.1 to 64.2 +/- 3.4%, respectively. There were no significant differences in intracellular pH for the three treatments. The results demonstrate that the differences in phosphocreatine concentration with varied FIO2 are not the result of different V(O2) onset kinetics, as this was eliminated by the experimental design. These data also demonstrate that changes in intracellular oxygenation, at the same work intensity, result in significant changes in cell homeostasis and thereby suggest a role for metabolic control by O2 even during submaximal exercise.
有证据表明，在稳态次最大运动期间，通过呼吸不同比例的吸入氧气（FIO2），高能磷酸代谢物的浓度可能会发生改变。虽然有人认为这些变化可能是由于在不同FIO2值下达到稳态氧气摄取量（V（O2））所需时间不同的结果，但我们推测它们是由于氧气张力的直接作用。我们在恒定负荷、稳态次最大运动期间使用31P磁共振波谱来确定：1）在相同的V（O2）下，不同FIO2时高能磷酸盐是否确实发生变化；2）这些变化不是由于V（O2）起始动力学的差异。六名男性受试者在1.5-T临床扫描仪中仰卧时进行了10分钟的稳态次最大跖屈运动[7.2±0.6（SE）W]。在运动前2分钟、运动期间10分钟和恢复期间6分钟连续收集磁共振波谱数据。受试者在恒定负荷下进行三次不同的运动回合，在10分钟运动回合的5分钟后切换FIO2。三种运动处理分别为：1）FIO2从0.1切换到0.21；2）FIO2从0.1切换到1.00；3）FIO2从1.00切换到0.1。对于所有三种处理，FIO2切换均显著（P≤0.05）改变了磷酸肌酸：1）从55.5±4.8到67.8±4.9%（相对于静息值）；2）从59.0±4.3到72.3±5.1%；3）分别从72.6±3.1到64.2±3.4%。三种处理的细胞内pH值没有显著差异。结果表明，不同FIO2时磷酸肌酸浓度的差异不是不同V（O2）起始动力学的结果，因为实验设计消除了这种差异。这些数据还表明，在相同工作强度下，细胞内氧合的变化会导致细胞内环境稳定的显著变化，从而表明即使在次最大运动期间，氧气在代谢控制中也发挥作用。
