Rassier Dilson E
Department of Kinesiology and Physical Education (Faculty of Education), McGill University, 475 Pine Avenue West, Montreal, Quebec, Canada.
Proc Biol Sci. 2008 Nov 22;275(1651):2577-86. doi: 10.1098/rspb.2008.0719.
When activated skeletal muscle is stretched, force increases in two phases. This study tested the hypothesis that the increase in stretch force during the first phase is produced by pre-power stroke cross bridges. Myofibrils were activated in sarcomere lengths (SLs) between 2.2 and 2.5 microm, and stretched by approximately 5-15 per cent SL. When stretch was performed at 1 microms-1SL-1, the transition between the two phases occurred at a critical stretch (SLc) of 8.4+/-0.85 nm half-sarcomere (hs)-1 and the force (critical force; Fc) was 1.62+/-0.24 times the isometric force (n=23). At stretches performed at a similar velocity (1 microms-1SL-1), 2,3-butanedione monoxime (BDM; 1 mM) that biases cross bridges into pre-power stroke states decreased the isometric force to 21.45+/-9.22 per cent, but increased the relative Fc to 2.35+/-0.34 times the isometric force and increased the SLc to 14.6+/-0.6 nm hs-1 (n=23), suggesting that pre-power stroke cross bridges are largely responsible for stretch forces.
当被激活的骨骼肌被拉伸时，力量分两个阶段增加。本研究检验了这样一个假设，即第一阶段拉伸力的增加是由动力冲程前的横桥产生的。肌原纤维在2.2至2.5微米的肌节长度（SL）下被激活，并被拉伸约5%-15%的SL。当以1微米·秒⁻¹·SL⁻¹的速度进行拉伸时，两个阶段之间的转变发生在半肌节（hs）为8.4±0.85纳米的临界拉伸（SLc）处，力（临界力；Fc）为等长力的1.62±0.24倍（n = 23）。在以相似速度（1微米·秒⁻¹·SL⁻¹）进行拉伸时，使横桥偏向动力冲程前状态的2,3-丁二酮单肟（BDM；1毫摩尔）将等长力降低至21.45±9.22%，但将相对Fc增加至等长力的2.35±0.34倍，并将SLc增加至14.6±0.6纳米·hs⁻¹（n = 23），这表明动力冲程前的横桥在很大程度上决定了拉伸力。
