Fall in intracellular PO2 at the onset of contractions in Xenopus single skeletal muscle fibers
Fall in intracellular PO2 at the onset of contractions in Xenopus single skeletal muscle fibers
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DOI：
10.1152/jappl.2001.90.5.1871
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发表时间：
2001-05-01
影响因子：
3.3
通讯作者：
Hogan, MC
中科院分区：
文献类型：
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作者：
Hogan, MC
它仍然不确定是否延迟启动的线粒体呼吸开始肌肉收缩与O-2的可用性。本研究的目的是测量的动力学下降的细胞内PO 2在一个收缩的工作期在休息和以前工作的单骨骼肌纤维的发病。从非洲爪蟾的蚓状肌中切下完整的单个骨骼肌纤维（n = 11），用O-2敏感探针注射，安装在玻璃室中，并在20 ℃下用林格溶液（PO 2 = 32 +/- 4 Torr和pH = 7.0）灌注。细胞内的PO 2测量在每个纤维在一个协议，依次组成的1分钟休息; 3分钟的强直收缩（1收缩/2秒）; 5分钟休息;最后，第二个3分钟的收缩期相同的第一。收缩期1和2的最大力发展和力的下降（最大力发展的83 +/- 2 vs. 86 +/- 3%）分别无显著差异。的时间延迟（收缩开始后细胞内PO 2开始下降前的时间）显著大于第一收缩期（P < 0.01）（13 +/- 3 s）与第二个相比（5 +/- 2 s），达到50%收缩稳态细胞内PO 2的时间（分别为28 +/- 5和18 +/- 4 s）。在非洲爪蟾单骨骼肌纤维中，1）收缩开始时细胞内PO 2下降的反应时间较长，表明除O-2可用性外的细胞内因素决定氧化磷酸化的开启动力学，2）先前的收缩期导致更快的开启动力学。
It remains uncertain whether the delayed onset of mitochondrial respiration on initiation of muscle contractions is related to O-2 availability. The purpose of this research was to measure the kinetics of the fall in intracellular PO2 at the onset of a contractile work period in rested and previously worked single skeletal muscle fibers. Intact single skeletal muscle fibers (n = 11) from Xenopus laevis were dissected from the lumbrical muscle, injected with an O-2-sensitive probe, mounted in a glass chamber, and perfused with Ringer solution (PO2 = 32 +/- 4 Torr and pH = 7.0) at 20 degreesC. Intracellular PO2 was measured in each fiber during a protocol consisting sequentially of 1-min rest; 3 min of tetanic contractions (1 contraction/2 s); 5-min rest; and, finally, a second 3-min contractile period identical to the first. Maximal force development and the fall in force (to 83 +/- 2 vs. 86 +/- 3% of maximal force development) in contractile periods 1 and 2, respectively, were not significantly different. The time delay (time before intracellular PO2 began to decrease after the onset of contractions) was significantly greater (P < 0.01) in the first contractile period (13 +/- 3 s) compared with the second (5 +/- 2 s), as was the time to reach 50% of the contractile steady-state intracellular PO2 (28 +/- 5 vs. 18 +/- 4 s, respectively). In Xenopus single skeletal muscle fibers, 1) the lengthy response time for the fall in intracellular PO2 at the onset of contractions suggests that intracellular factors other than O-2 availability determine the on-kinetics of oxidative phosphorylation and 2) a prior contractile period results in more rapid on-kinetics.