Williams J H, Ward C W, Spangenburg E E, Nelson R M
Muscular Function Laboratory, Department of Human Nutrition, Foods, and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0430, USA.
J Appl Physiol (1985). 1998 Aug;85(2):619-26. doi: 10.1152/jappl.1998.85.2.619.
This study examined the effects of fatigue on the functional aspects of the contractile apparatus and sarcoplasmic reticulum (SR). Frog semitendinosus muscles were stimulated to fatigue, and skinned fibers or a homogenate fraction was prepared from both fatigued and rested contralateral muscles. In fatigued fibers, maximal Ca2+-activated force of the contractile apparatus was unaltered, whereas maximal actomyosin-ATPase activity was depressed by 20%. The Ca2+ sensitivity of force was increased, whereas that of actomyosin-ATPase was not altered. Also, the rate constant for tension redevelopment was decreased at submaximal Ca2+ concentration. These latter findings suggest that fatigue slows the dissociation of force-generating myosin cross bridges. Ca2+ uptake and Ca2+-ATPase activity of the SR were depressed by 46 and 21%, respectively, in the fatigued muscles. Fatigue also reduced the rates of SR Ca2+ release evoked by AgNO3 and 4-chloro-m-cresol by 38 and 45%, respectively. During fatigue, the contractile apparatus and SR undergo intrinsic functional alterations. These changes likely result in altered force production and energy consumption by the intact muscle.
本研究考察了疲劳对收缩装置和肌浆网（SR）功能方面的影响。刺激青蛙半腱肌使其疲劳，然后从疲劳和未疲劳的对侧肌肉制备去皮纤维或匀浆组分。在疲劳纤维中，收缩装置的最大Ca2+激活力未改变，而最大肌动球蛋白ATP酶活性降低了20%。力的Ca2+敏感性增加，而肌动球蛋白ATP酶的Ca2+敏感性未改变。此外，在亚最大Ca2+浓度下，张力重建的速率常数降低。这些结果表明，疲劳会减缓产生力的肌球蛋白横桥的解离。疲劳肌肉中，SR的Ca2+摄取和Ca2+-ATP酶活性分别降低了46%和21%。疲劳还分别使由AgNO3和4-氯间甲酚诱发的SR Ca2+释放速率降低了38%和45%。在疲劳过程中，收缩装置和SR会发生内在功能改变。这些变化可能导致完整肌肉的力产生和能量消耗发生改变。
