SOME ELECTRICAL AND MECHANICAL EFFECTS OF STRONTIUM ON TOAD VENTRICULAR MUSCLE - COMPARISON TO CALCIUM
SOME ELECTRICAL AND MECHANICAL EFFECTS OF STRONTIUM ON TOAD VENTRICULAR MUSCLE - COMPARISON TO CALCIUM
复制标题
DOI：
10.1113/jphysiol.1975.sp011158
复制
发表时间：
1975-01-01
影响因子：
5.5
通讯作者：
VANBAAL, S
中科院分区：
文献类型：
--
作者：
BASS, BG;CIULLA, EM;VANBAAL, S
本实验观察了锶的机械和电生理效应，并与钙的作用进行了比较。在对照(2 MM)到10 mM的浓度范围内，通过用等摩尔浓度的锶代替钙，或者通过保持恒定的总钙和锶浓度(其中单个钙和锶浓度不同)来比较钙和锶的影响。通过等长收缩的最大dt/dt[时间]、非常轻负荷的等张收缩的最大dL/dt[长度]和后负荷的力-速度曲线的形状来评估收缩激活程度的变化，特别注意曲线在速度轴上接近Vmax时的形状。通过跨膜动作电位的变化(用玻璃微电极记录)和与其在两栖动物脑室持续时间直接相关的力学参数的变化来评估对细胞膜的影响。等长张力和等张缩短的持续时间。同时记录等长张力和动作电位。在高于对照浓度时，钙和锶对dT/dt和dL/dt的影响相似，但不相同。在等摩尔浓度下，两种离子单独作用或在总钙和锶浓度不变时，两种离子共同作用时，dt/dt和dL/dt增大，力-速度曲线上移。在总钙和锶浓度不变的情况下，当力-速度曲线接近速度截止点时，它们实际上是可重叠的。在高于对照浓度时，锶使动作电位时程明显延长，钙使动作电位时程明显缩短。与dT/dT和dL/dT不同，等长拉伸和等张缩短的总持续时间取决于一定总浓度内的特定钙和锶浓度，并随着锶浓度的增加而逐渐延长。钙和锶对dT/dT、dL/dT以及轻载时力-速度关系的影响与钙离子的存在有关。单用锶时，dt/dt和dL/dt较等摩尔浓度的钙快，达峰时间延长。仅在锶中的力-速度曲线一直向上移动，超过其他有钙存在的曲线。这两种离子之间的差异部分归因于高钙时动作电位的快速和早期复极化，以及由此产生的活跃状态下的积聚和较慢的dt/dt和dl/dt。钙和锶激活收缩的方式相似，尽管不同，但在细胞膜上是竞争的。
The mechanical and electrophysiological effects of Sr were evaluated and compared to those of Ca in isolated, electrically driven toad ventricular muscle strips. The effects of Ca and Sr were compared at concentrations from control (2 mM) to 10 mM either by substitution of Sr for Ca at equimolar concentration, or by maintenance of a constant total Ca plus Sr concentration within which individual Ca and Sr concentrations were varied. Changes in the degree of contractile activation were evaluated in terms of changes in maximal dT/dt [time] of isometric contractions, maximal dL/dt [length] of very lightly loaded isotonic contractions, and the shape of after-loaded force-velocity curves, with specific attention directed to the shape of the curves as they approached Vmax on the velocity axis. Effects on the cell membrane were evaluated in terms of changes in the transmembrane action potential (recorded with glass micro-electrodes) and in the mechanical parameters directly related to its duration in the amphibian ventricle, viz. the duration of isometric tension and isotonic shortening. Isometric tension and action potentials were recorded simultaneously. Ca and Sr, at concentrations above control, had similar but not identical effects on dT/dt and dL/dt. Both ions alone in equimolar concentrations, or together at constant total Ca plus Sr concentration, increased dT/dt and dL/dt and shifted force-velocity curves upward. At constant total Ca plus Sr concentration, force-velocity curves were virtually superimposable as they approached the velocity intercept. The duration of the action potential was markedly prolonged by Sr and shortened by Ca in concentrations above control. Unlike dT/dt and dL/dt, the total duration of isometric tension and isotonic shortening depended upon the specific Ca and Sr concentrations within a constant total concentration, and were progressively prolonged as the Sr concentration was increased. The similar effects of Ca and Sr on dT/dt, dL/dt, and on the force-velocity relationship at light loads depended upon the presence of Ca2+. In Sr alone, dT/dt and dL/dt were faster than in an equimolar concentration of Ca, and time to maximal dT/dt and dL/dt was prolonged. The force-velocity curve in Sr alone was consistently shifted upward beyond the other curves in which Ca was present. These differences between the 2 ions are attributed in part to the rapid and early repolarization of the action potential in elevated Ca and the resultant abbreviation of the build up in active state and slower dT/dt and dL/dt. Ca and Sr act in a similar although not identical way in activating contraction but are competitive at the cell membrane.