Effect of physiological levels of caffeine on Ca2+ handling and fatigue development in Xenopus isolated single myofibers.
Effect of physiological levels of caffeine on Ca2+ handling and fatigue development in Xenopus isolated single myofibers.
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咖啡因生理水平对非洲爪蟾分离单肌纤维 Ca2 处理和疲劳发展的影响。
DOI：
10.1152/ajpregu.90901.2008
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
Hogan,MichaelC
中科院分区：
文献类型：
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作者：
Rosser,JoelleI;Walsh,Brandon;Hogan,MichaelC
本研究的目的是确定暴露于外源生理浓度的咖啡因是否影响分离的单爪爪蟾骨骼肌纤维的收缩性、Ca2+处理和疲劳发展。分离后，在 20°C 下对每根肌纤维 (n= 8) 进行两个相同的收缩期（间隔 60 分钟休息）。在第一个收缩期，四根纤维用不含咖啡因的林格溶液灌注，而其他四根纤维用含咖啡因的（70 μM）林格溶液灌注。第二个收缩期的顺序相反。在每个收缩期，以递增的频率（0.16、0.20、0.25、0.33、0.50 和 1.0 强直收缩/秒）刺激单根肌纤维，每个刺激频率持续 2 分钟，直到疲劳发生，在本研究中定义为张力发展下降至最大值的 66%。同时测量张力发展和游离胞质 [Ca2+]（fura-2 荧光光谱）。不含咖啡因和含咖啡因的试验之间，峰值力产生、疲劳时间、胞质 Ca2+ 水平或松弛时间没有显着差异。这些结果表明，生理水平的咖啡因对爪蟾单肌纤维收缩性、Ca2+处理和疲劳发展没有显着影响，并表明生理水平的咖啡因对中高强度收缩期间肌肉性能的任何增效作用可能与肌纤维无关的因素有关。
The purpose of the present study was to determine whether exposure to exogenous physiological concentrations of caffeine influence contractility, Ca2+handling, and fatigue development in isolated singleXenopus laevisskeletal muscle fibers. After isolation, two identical contractile periods (separated by 60-min rest) were conducted in each single myofiber (n= 8) at 20°C. During the first contractile period, four fibers were perfused with a noncaffeinated Ringer solution, while the other four fibers were perfused with a caffeinated (70 μM) Ringer solution. The order was reversed for the second contractile period. The single myofibers were stimulated during each contractile period at increasing frequencies (0.16, 0.20, 0.25, 0.33, 0.50, and 1.0 tetanic contractions/s), with each stimulation frequency lasting 2 min until fatigue ensued, defined in this study as a fall in tension development to 66% of maximum. Tension development and free cytosolic [Ca2+] (fura-2 fluorescence spectroscopy) were simultaneously measured. There was no significant difference in the peak force generation, time to fatigue, cytosolic Ca2+levels, or relaxation times between the noncaffeinated and caffeinated trials. These results demonstrate that physiological levels of caffeine have no significant effect onXenopussingle myofiber contractility, Ca2+handling, and fatigue development, and suggest that any ergogenic effects of physiological levels of caffeine on muscle performance during contractions of moderate to high intensity are likely related to factors extraneous to the muscle fiber.