Nesher R, Karl I E, Kaiser K E, Kipnis D M
Am J Physiol. 1980 Dec;239(6):E454-60. doi: 10.1152/ajpendo.1980.239.6.E454.
An in vitro rat muscle preparation is described that can contract at rates of 12-240 twitches/min. Maximum dF/dt paralleled maximum twitch tension, their ratio being constant at approximately 8 ms for contraction rates of 12-120 twitches/min. Time to peak tension was 8-13 ms, time to peak dF/dt 5-8 ms, and half-relaxation time 4 ms. These parameters were unaffected by rate of contraction or duration of isometric work. Differential ATPase staining demonstrated that 60-65% of the fibers were fast-twitch white, 20% fast-twitch red, and 15% slow-twitch red. The preponderance of fast-twitch fibers correlated with the observed mechanical performance of the muscle. Muscles contracting for 60 min at rates up to 48 twitches/min maintained total adenine nucleotide content (ATP, ADP, AMP) at near resting levels. At higher twitch rates (72-240 twitches/min), total adenine nucleotide content decreased 40%, reflecting exclusively a fall in ATP in the presence of adequate phosphocreatine stores. Adequate oxygenation was reflected by lactate-to-pyruvate ratios in the range of 11-15 at all rates of contraction.
本文描述了一种体外大鼠肌肉制备方法，该肌肉能以12 - 240次抽搐/分钟的速率收缩。最大dF/dt与最大抽搐张力平行，在12 - 120次抽搐/分钟的收缩速率下，它们的比值在约8毫秒时保持恒定。达到峰值张力的时间为8 - 13毫秒，达到峰值dF/dt的时间为5 - 8毫秒，半松弛时间为4毫秒。这些参数不受收缩速率或等长工作持续时间的影响。ATP酶差异染色显示，60 - 65%的纤维为快肌白肌，20%为快肌红肌，15%为慢肌红肌。快肌纤维占优势与观察到的肌肉力学性能相关。以高达48次抽搐/分钟的速率收缩60分钟的肌肉，总腺嘌呤核苷酸含量（ATP、ADP、AMP）维持在接近静息水平。在较高的抽搐速率（72 - 240次抽搐/分钟）下，总腺嘌呤核苷酸含量下降40%，这完全反映了在磷酸肌酸储备充足的情况下ATP的下降。在所有收缩速率下，乳酸与丙酮酸的比值在11 - 15范围内，这反映了充足的氧合作用。
