Calcium‐activated force responses in fast‐ and slow‐twitch skinned muscle fibres of the rat at different temperatures.
Calcium‐activated force responses in fast‐ and slow‐twitch skinned muscle fibres of the rat at different temperatures.
复制标题
不同温度下大鼠快肌和慢肌纤维的钙激活力反应。
DOI：
--
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
D. Williams
中科院分区：
文献类型：
--
作者：
D. Stephenson;D. Williams
1.在制备物中Ca 2+浓度突然变化后，在3 - 35 ℃范围内的不同温度下测量了大鼠骨骼肌（趾长伸肌和比目鱼肌）机械剥皮纤维的力响应。2.在所有温度下，慢缩肌纤维和快缩肌纤维在相对稳态力-[Ca 2 +]关系方面存在特征性差异：例如慢缩肌纤维的激活[Ca 2 +]阈值较低，力-pCa曲线不太陡峭。3.在3 - 5 ℃时，两种类型肌纤维的力变化明显滞后于制剂中[Ca 2 +]的估计变化，这使我们能够对两种肌纤维类型力发展过程中的Ca 2+动力学进行比较分析。该分析表明，两个和六个Ca 2+离子分别参与慢肌纤维和快肌纤维收缩的调节单元。4.在5摄氏度下，[Ca 2 +]突然下降后的松弛速率在慢收缩肌肉中比在快收缩肌肉中低得多，这表明收缩装置的特性可以在体内确定松弛速率方面发挥重要作用。5.在每个温度下，来自不同动物的相同类型的肌纤维之间的Ca 2+敏感性存在很大差异。然而，对于相同类型的所有纤维，力-[Ca 2 +]关系的陡度基本相同。6.从5到25摄氏度的温度变化对快缩肌纤维的敏感性有统计学显著影响，使它们对Ca 2+的敏感性降低2倍。然而，温度从25 ℃进一步升高到35 ℃，对快缩肌纤维中的力-[Ca 2 +]关系没有任何统计学显著影响。7.温度对慢收缩肌纤维的Ca 2+敏感性的影响在统计学上不显著，主要是因为这些制剂在室温下的敏感性差异很大。8.在25和35 ℃下亚最大激活（小于60%最大力）时，在所有慢收缩肌纤维的力反应中观察到两种与细胞内膜无关的振荡过程，但在3 - 5 ℃下从未观察到。振荡频率随温度升高而增加。9.两种肌纤维类型中的最大Ca 2+激活力在很大程度上取决于0 - 25 ℃范围内的温度，但仅在25 ℃以上略微增加。10.在僵直状态下的实验表明，当温度降低到25 ℃以下时，可能的肌动球蛋白相互作用位点的数量大大减少。
1. Force responses from mechanically skinned fibres of rat skeletal muscles (extensor digitorum longus and soleus) were measured at different temperatures in the range 3‐35 degrees C following sudden changes in Ca2+ concentration in the preparations. 2. At all temperatures there were characteristic differences between the slow‐ and fast‐twitch muscle fibres with respect to the relative steady‐state force‐[Ca2+] relation: such as a lower [Ca2+] threshold for activation and a less steep force‐pCa curve in slow‐twitch muscle fibres. 3. At 3‐5 degrees C the force changes in both types of muscle fibres lagged considerably behind the estimated changes in [Ca2+] within the preparations and this enabled us to perform a comparative analysis of the Ca2+ kinetics in the process of force development in both muscle fibre types. This analysis suggest that two and six Ca2+ ions are involved in the regulatory unit for contraction of slow‐ and fast‐twitch muscle fibres respectively. 4. The rate of relaxation following a sudden decrease in [Ca2+] was much lower in the slow‐twitch than in the fast‐twitch muscle at 5 degrees C, suggesting that properties of the contractile apparatus could play an essential role in determining the rate of relaxation in vivo. 5. There was substantial variation in Ca2+ sensitivity between muscle fibres of the same type from different animals at each temperature. However the steepness of the force‐[Ca2+] relation was essentially the same for all fibres of the same type. 6. A change in temperature from 5 to 25 degrees C had a statistically significant effect on the sensitivity of the fast‐twitch muscle fibres, rendering them less sensitive to Ca2+ by a factor of 2. However a further increase in temperature from 25 to 35 degrees C did not have any statistically significant effect on the force‐[Ca2+] relation in fast‐twitch muscle fibres. 7. The effect of temperature on the Ca2+ sensitivity of slow‐twitch muscle fibres was not statistically significant, mainly because of the large variation in sensitivity amongst these preparations at room temperature. 8. Two types of oscillatory processes not associated with intracellular membranes were observed in the force response of all slow‐twitch muscle fibres when submaximally activated (less than 60% maximum force) at 25 and 35 degrees C, but never at 3‐5 degrees C. The frequency of oscillations increased with temperature. 9. Maximum Ca2+‐activated force in both muscle fibre types was greatly dependent upon temperature over the range 0‐25 degrees C, but increased only slightly above 25 degrees C. 10. Experiments on the rigor state suggest that the number of possible actomyosin interacting sites diminishes considerably as temperature is decreased below 25 degrees C.