This study investigated the effect of S-glutathionylation on passive force in skeletal muscle fibres, to determine whether activity-related redox reactions could modulate the passive force properties of muscle. Mechanically-skinned fibres were freshly obtained from human and rat muscle, setting sarcomere length (SL) by laser diffraction. Larger stretches were required to produce passive force in human fibres compared to rat fibres, but there were no fibre-type differences in either species. When fibres were exposed to glutathione disulfide (GSSG; 20 mM, 15 min) whilst stretched (at a SL where passive force reached ~ 20% of maximal Ca²⁺-activated force, denoted as SL_{20 % max}), passive force was subsequently decreased at all SLs in both type I and type II fibres of rat and human (e.g., passive force at SL_{20 % max} decreased by 12 to 25%). This decrease was fully reversed by subsequent reducing treatment with dithiothreitol (DTT; 10 mM for 10 min). If freshly skinned fibres were initially treated with DTT, there was an increase in passive force in type II fibres (by 10 ± 3% and 9 ± 2% in rat and human fibres, respectively), but not in type I fibres. These results indicate that (i) S-glutathionylation, presumably in titin, causes a decrease in passive force in skeletal muscle fibres, but the reduction is relatively smaller than that reported in cardiac muscle, (ii) in rested muscle in vivo, there appears to be some level of reversible oxidative modification, probably involving S-glutathionylation of titin, in type II fibres, but not in type I fibres.

本研究调查了S-谷胱甘肽化对骨骼肌纤维被动力的影响，以确定与活动相关的氧化还原反应是否可以调节肌肉的被动力特性。从人和大鼠肌肉中新鲜获得机械剥皮纤维，通过激光衍射设置肌节长度 (SL)。与大鼠纤维相比，人的纤维需要更大的拉伸才能产生被动力，但两种物种的纤维类型没有差异。当纤维暴露于二硫化谷胱甘肽（GSSG；20 mM，15 分钟）同时拉伸时（在 SL 处，被动力达到最大 Ca ²⁺激活力的~ 20% ，表示为 SL _{20% max})，随后在大鼠和人类的 I 型和 II 型纤维中，所有 SL 处的被动力都降低了（例如，SL_{最大 20%}处的被动力降低了 12% 至 25%）。通过随后用二硫苏糖醇（DTT；10 mM，10 分钟）进行还原处理，这种降低被完全逆转。如果刚剥皮的纤维最初用 DTT 处理，II 型纤维的被动力会增加（大鼠和人纤维分别增加 10 ± 3% 和 9 ± 2%），但 I 型纤维没有。这些结果表明 (i) S- 谷胱甘肽化，大概是在肌联蛋白中，导致骨骼肌纤维被动力的减少，但减少程度比在心肌中报告的要小，(ii) 在体内静息肌肉中，似乎存在某种程度的可逆氧化修饰，可能涉及肌联蛋白的S-谷胱甘肽化，在 II 型纤维中，但在 I 型纤维中不涉及。