Gilliver S F, Jones D A, Rittweger J, Degens H
Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, John Dalton Building, Oxford Road, Manchester M5 1GD, UK.
J Musculoskelet Neuronal Interact. 2010 Dec;10(4):267-73.
Oxidation alters calcium sensitivity, and decreases maximum isometric force (Po) and shortening velocity (Vmax) of single muscle fibres. To examine the effect of oxidation on the curvature of the force-velocity relationship, which determines muscle power in addition to Po and Vmax, skinned rat type I fibres were maximally activated at 15°C in a solution with pCa 4.5 and subjected to isotonic contractions before and after 4-min incubation in 50 mM H₂O₂ (n=10) or normal relaxing solution (n=3). In five oxidised and four control fibres the rate of force redevelopment (ktr), following a rapid release and re-stretch, was measured. This gives a measure of the sum of the rate constants for cross-bridge attachment (f) and detachment (g₁): (f+g₁). H₂O₂ reduced Po, Vmax and ktr by 19%, 21% and 24% respectively (P<0.001), while the shape of the force-velocity relationship was unchanged. Fitting data to the Huxley cross-bridge model suggested that oxidation decreased both the rate constant for cross-bridge attachment (f), and detachment of negatively strained cross-bridges (g₂), similar to the effect of reduced activation. This suggests that oxidative modification is a possible cause of the variation in contractile properties between muscle fibres of the same type.
氧化作用会改变钙敏感性，并降低单根肌纤维的最大等长力（Po）和缩短速度（Vmax）。为了研究氧化作用对力-速度关系曲线的影响（力-速度关系曲线除了决定Po和Vmax外，还决定肌肉功率），将去皮肤的大鼠I型纤维在15°C下于pCa 4.5的溶液中最大程度激活，并在50 mM H₂O₂中孵育4分钟之前和之后进行等张收缩（n = 10），或在正常松弛溶液中进行等张收缩（n = 3）。在5根氧化纤维和4根对照纤维中，测量了快速释放和重新拉伸后力的重新发展速率（ktr）。这给出了横桥附着（f）和解离（g₁）速率常数之和（f + g₁）的量度。H₂O₂使Po、Vmax和ktr分别降低了19%、21%和24%（P < 0.001），而力-速度关系曲线的形状未改变。将数据拟合到赫胥黎横桥模型表明，氧化作用降低了横桥附着的速率常数（f）以及负应变横桥的解离速率（g₂），这与激活降低的效果相似。这表明氧化修饰可能是同一类型肌纤维收缩特性变化的一个原因。
