Walters Thomas J, Kragh John F, Baer David G
United States Army Institute of Surgical Research, Fort Sam Houston, TX 78234-6315, USA.
Appl Physiol Nutr Metab. 2008 Apr;33(2):272-81. doi: 10.1139/H07-180.
This study was designed to determine if previously reported differences in the functional impairment of muscles composed of predominantly different fiber types occurs following extended periods of ischemia. We hypothesized that the soleus (Sol) muscle, a predominantly slow-twitch muscle, would be less vulnerable to tourniquet-induced ischemia-reperfusion than the plantaris (Plant), a predominantly fast-twitch muscle, as determined by the assessment of isometric contractile function. Male Sprague-Dawley rats were assigned to one of the following groups to undergo tourniquet application (TKA) (n = 6/group): 2 h TKA, 2 d recovery; 4 h TKA, 2 d recovery; 2 h TKA, 14 d recovery; or 4 h TKA, 14 d recovery. In situ isometric contractile properties were assessed in the predominantly slow-twitch Sol and the predominantly fast-twitch Plant; the contralateral muscle served as the internal control. At 2 d, muscle contraction could not be elicited via neural stimulation, but muscles did contract with direct stimulation, which indicates neural injury. This condition was resolved by day 14. At this time point, tetanic tension (Po) in the Plant was reduced by 45% and 69% in the 2 and 4 h groups, respectively. Po for the Sol was unaffected in the 2 h group, but was reduced by 30% in the 4 h group. The fatigue resistance of the Plant was increased 2 fold in the 4 h group and was unchanged in all other groups. These results demonstrate that vulnerability to tourniquet-induced ischemia-reperfusion injury is dramatically different with respect to muscle fiber-type composition.
本研究旨在确定在长时间缺血后，先前报道的由主要不同纤维类型组成的肌肉功能损伤差异是否会出现。我们假设，比目鱼肌（Sol）作为主要的慢肌，在止血带诱导的缺血再灌注中比跖肌（Plant）更不容易受到损伤，跖肌是主要的快肌，这是通过等长收缩功能评估来确定的。将雄性Sprague-Dawley大鼠分为以下几组接受止血带应用（TKA）（每组n = 6）：2小时TKA，恢复2天；4小时TKA，恢复2天；2小时TKA，恢复14天；或4小时TKA，恢复14天。在主要为慢肌的比目鱼肌和主要为快肌的跖肌中评估原位等长收缩特性；对侧肌肉作为内部对照。在2天时，通过神经刺激无法引发肌肉收缩，但肌肉在直接刺激下确实会收缩，这表明神经损伤。这种情况在第14天时得到解决。在这个时间点，2小时组和4小时组中跖肌的强直张力（Po）分别降低了45%和69%。2小时组中比目鱼肌的Po未受影响，但4小时组中降低了30%。4小时组中跖肌的抗疲劳能力增加了2倍，其他所有组均未改变。这些结果表明，对于止血带诱导的缺血再灌注损伤的易感性在肌肉纤维类型组成方面存在显著差异。
