Kobayashi T, Kosuge S, Narushima K, Sugi H
Department of Physiology, School of Medicine, Teikyo University, Tokyo, Japan.
Biochem Biophys Res Commun. 1998 Aug 10;249(1):161-5. doi: 10.1006/bbrc.1998.9117.
When tetanized frog skeletal muscle fibers are subjected to moderate-velocity stretches (< 1 L0/s), the tension developed above the level of isometric tension starts to decay after a sudden reduction of stretch velocity by more than 40-50%, though the fibers are still being stretched. We analysed the decay of tension response caused by the sudden reduction of stretch velocity, by applying three different types of stretch to a tetanized fiber, i.e., a 1.5% stretch with velocity V1 (stretch-1), a 1.5% stretch with velocity V2 < V1 (stretch-2), and a 3% stretch consisting of stretch-1 and stretch-2 applied in succession (stretch-3) and comparing the corresponding tension responses, TR-1, TR-2, and TR-3. It was found that TR-3 to stretch-3 resulted from algebraical summation of TR-1 to the preceding stretch-1 and TR-2 to the subsequent stretch-2. These results can be accounted for by assuming two distinct cross-bridge populations in stretched fibers.
当强直收缩的青蛙骨骼肌纤维受到中等速度拉伸（<1L0/s）时，在拉伸速度突然降低超过40 - 50%后，高于等长张力水平产生的张力开始衰减，尽管纤维仍在被拉伸。我们通过对强直收缩的纤维施加三种不同类型的拉伸，即速度为V1的1.5%拉伸（拉伸-1）、速度V2<V1的1.5%拉伸（拉伸-2）以及由拉伸-1和拉伸-2连续施加组成的3%拉伸（拉伸-3），并比较相应的张力响应TR-1、TR-2和TR-3，分析了拉伸速度突然降低引起的张力响应衰减。结果发现，对拉伸-3的TR-3是由对前一个拉伸-1的TR-1和对后续拉伸-2的TR-2代数求和得出的。这些结果可以通过假设拉伸纤维中存在两种不同的横桥群体来解释。
