Effects of calcium and ionic strength on shortening velocity and tension development in frog skinned muscle fibres.
Effects of calcium and ionic strength on shortening velocity and tension development in frog skinned muscle fibres.
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DOI：
10.1113/jphysiol.1981.sp013580
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发表时间：
1981-02
期刊：
影响因子：
--
通讯作者：
F. Julian;R. Moss
中科院分区：
文献类型：
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作者：
F. Julian;R. Moss
1.在1-10℃温度范围内，研究了钙离子浓度和离子强度对蛙皮肌肉纤维最大缩短速度(Vmax)和张力产生能力的影响。2.纤维段安装在力传感器和伺服电机之间，可通过显微镜观察和拍摄。在激活过程中条纹变得不均匀的片段被丢弃。3.通过将张力阶跃到小于恒定等长张力的值，得到作为载荷的函数的速度。然后通过外推技术确定Vmax。VMAX也是使用第二种独立的方法获得的，方法是测量占用施加在数据段上的各种空闲时间所需的时间。4.钙离子浓度对Vmax有显著影响，当钙离子浓度降低到稳定张力小于一半时，Vmax下降约一半。5.Vmax不受离子强度变化的影响，在0.09-0.18M范围内，稳态张力随离子强度的降低而增加。6.这些结果表明，离子强度的变化影响的是连接的交叉桥的数目或硬度，而离子强度对肌动蛋白-肌球蛋白在无负荷缩短过程中的稳态相互作用动力学没有明显的影响。钙离子对Vmax的影响机制尚不清楚，但对其可能的作用部位进行了讨论。
1. The influence of Ca2+ concentration and ionic strength on the maximum velocity of shortening (Vmax) and the tension generating capability of frog skinned muscle fibres has been studied at temperatures between 1 and 10 degrees C. 2. Fibre segments were mounted between a force transducer and servo motor, where they could be viewed and photographed through a microscope. Segments in which the striations became non‐uniform during activation were discarded. 3. Velocity was obtained as a function of load by stepping the tension to values less than the steady isometric tension. Vmax was then determined by an extrapolation technique. Vmax was also obtained using a second, independent method by measuring the times required to take up various amounts of slack imposed on the segments. 4. Vmax was significantly influenced by the Ca2+ concentration, decreasing by about one half when the Ca2+ concentration was reduced to give steady tensions less than half‐maximal. 5. Vmax was not influenced by changes in ionic strength, in the range 0.09‐0.18 M. Steady tension was found to increase as ionic strength was decreased in the same range. 6. These results indicate that the effect of changes in ionic strength is to alter the numbers or stiffness of attached cross‐bridges, while there is no apparent influence of ionic strength on the steady‐state kinetics of the actin‐myosin interaction during unloaded shortening. The mechanism responsible for the influence of Ca2+ on Vmax is unknown, though possible sites of action for Ca2+ are discussed.