The tension and sarcomere length responses induced by ramp stretches (at amplitudes of 1-3 % fibre length (Lo) and speeds of 0.01-12 Lo s-1) were examined at different temperatures (range, 10-35 degrees C) in resting intact muscle fibre bundles isolated from the soleus (a slow-twitch muscle) and extensor digitorum longus (a fast-twitch muscle) of the rat. Some observations are also presented on the effects of chemical skinning on passive viscoelasticity at 10 degrees C. 2. As previously reported, the tension response to a ramp stretch, in different preparations and under various conditions, could be resolved into a viscous (P1), a viscoelastic (P2) and an elastic (P3) component and showed characteristic differences between slow and fast muscle fibres. 3. Chemical skinning of the muscle fibres led to a decrease in the amplitude of all three tension components. However, the fast-slow fibre differences remained after skinning. For example, the viscosity coefficient derived from P1 tension data decreased from 0.84 +/- 0.06 before skinning to 0.44 +/- 0.06 kN s m-2 after skinning in fast fibres; the corresponding values in slow fibres were 2.1 +/- 0.08 and 0.87 +/- 0.09 kN s m-2, respectively. 4. Increasing the experimental temperature from 10 to 35 degrees C led to a decrease in all the tension components in both fast and slow muscle fibre bundles. The decrease of P1 (viscous) tension was such that the viscosity coefficient calculated using P1 data was reduced from 0.84 +/- 0.1 to 0.43 +/- 0.05 kN s m-2 in fast fibres and from 2.0 +/- 0.1 to 1.0 +/- 0.1 kN s m-2 in slow fibres (Q10 of approximately 1.3 in both). 5. In both fast and slow muscle fibre preparations, the plateau tension of the viscoelastic component (P2) decreased by 60-80 % as the temperature was increased from 10 to 35 degrees C giving P2 tension a Q10 of approximately 1.4 in slow fibres and approximately 1.7 in the fast fibres. Additionally, the relaxation time of the viscoelasticity decreased from 11.9 +/- 1 ms (fast) and 43.1 +/- 1 ms (slow) at 10 degrees C to 3 +/- 0.5 ms (fast) at 25 C degrees and 8. 7 +/- 0.6 ms (slow) at 35 degrees C (Q10 of approximately 2.0 in slow and approximately 2.5 in fast fibres). 6. The fast-slow fibre differences in passive viscoelasticity remained at the high physiological temperatures. The physiological significance of such fibre-type differences and their possible underlying mechanisms are discussed.
摘要
在不同温度（10 - 35摄氏度范围）下，对从大鼠比目鱼肌（慢肌）和趾长伸肌（快肌）分离出的静息完整肌纤维束，研究了斜坡拉伸（幅度为纤维长度（Lo）的1 - 3%，速度为0.01 - 12 Lo s⁻¹）诱导的张力和肌节长度反应。还给出了一些关于在10摄氏度下化学去皮对被动粘弹性影响的观察结果。2. 如先前报道，在不同制剂和各种条件下，对斜坡拉伸的张力反应可分解为粘性（P1）、粘弹性（P2）和弹性（P3）成分，并且在慢肌纤维和快肌纤维之间表现出特征差异。3. 肌纤维的化学去皮导致所有三个张力成分的幅度降低。然而，去皮后快 - 慢纤维差异仍然存在。例如，从P1张力数据得出的粘度系数在快肌纤维中从去皮前的0.84±0.06降至去皮后的0.44±0.06 kN s m⁻²；慢肌纤维中的相应值分别为2.1±0.08和0.87±0.09 kN s m⁻²。4. 将实验温度从10摄氏度提高到35摄氏度导致快肌和慢肌纤维束中的所有张力成分均降低。P1（粘性）张力的降低使得使用P1数据计算的粘度系数在快肌纤维中从0.84±0.1降至0.43±0.05 kN s m⁻²，在慢肌纤维中从2.0±0.1降至1.0±0.1 kN s m⁻²（两者的Q10约为1.3）。5. 在快肌和慢肌纤维制剂中，随着温度从10摄氏度升高到35摄氏度，粘弹性成分（P2）的平台张力降低了60 - 80%，慢肌纤维中P2张力的Q10约为1.4，快肌纤维中约为1.7。此外，粘弹性的弛豫时间从10摄氏度时的11.9±1毫秒（快肌）和43.1±1毫秒（慢肌）降至25摄氏度时的3±0.5毫秒（快肌）和35摄氏度时的8.7±0.6毫秒（慢肌）（慢肌纤维的Q10约为2.0，快肌纤维约为2.5）。6. 在高生理温度下，被动粘弹性的快 - 慢纤维差异仍然存在。讨论了这种纤维类型差异的生理意义及其可能的潜在机制。
