Saeki Y, Kato C, Horikoshi T, Yanagisawa K
Pflugers Arch. 1984 Mar;400(3):235-40. doi: 10.1007/BF00581553.
At a muscle length, L0 (just taut), isometric tension and tension transients in response to rapid step stretches in length (mostly less than 1.2% of L0 within 2 ms) were measured at constant levels of Ba2+ activation of varying magnitude in glycerinated cat right-ventricular papillary muscles (2-3 mm long, 130-200 micron in diameter). The majority of the experiments were carried out at room temperature (26-27 degrees C) and at a pH of 6.8. The steady isometric tension increased as Ba2+ was varied from slightly below pBa 6 to about pBa 4. The concentration range of Ba2+-activated muscle was roughly 10 times higher than that of Ca2+-activated muscle. Maximum Ba2+-activated isometric tension was 79.0 +/- 4.2% (mean +/- SD, n = 8) of that activated with Ca2+. The tension transients in Ba2+-activated muscle were characterized by at least three distinct phases; an immediate tension increase coincident with the stretch, a rapid exponential tension decrease (time constant, tau 1 = 7.3 +/- 1.0 ms, n = 5) and a delayed exponential tension rise (tau 2 = 104 +/- 5.7 ms, n = 5). The profile of tension response was quite similar to that of Ca2+-activated muscle. These results suggest that in Ba2+-activated glycerinated heart muscle the cross-bridge turnover is taking place as in the Ca2+-activated muscle, but the number of active cross-bridges at maximally activated state is smaller than that of Ca2+-activated muscle.
在甘油化的猫右心室乳头肌（长2 - 3毫米，直径130 - 200微米）中，在不同强度的Ba²⁺激活的恒定水平下，于肌肉长度L0（刚好绷紧）时，测量了等长张力以及对长度快速阶跃拉伸（在2毫秒内大多小于L0的1.2%）的张力瞬变。大多数实验在室温（26 - 27摄氏度）和pH值为6.8的条件下进行。随着Ba²⁺从略低于pBa 6变化到约pBa 4，稳定的等长张力增加。Ba²⁺激活肌肉的浓度范围大约比Ca²⁺激活肌肉高10倍。最大Ba²⁺激活的等长张力为Ca²⁺激活时的79.0±4.2%（平均值±标准差，n = 8）。Ba²⁺激活肌肉中的张力瞬变至少有三个不同阶段；与拉伸同时出现的立即张力增加、快速指数式张力下降（时间常数，τ1 = 7.3±1.0毫秒，n = 5）以及延迟的指数式张力上升（τ2 = 104±5.7毫秒，n = 5）。张力响应的曲线与Ca²⁺激活肌肉的非常相似。这些结果表明，在Ba²⁺激活的甘油化心肌中，横桥周转与Ca²⁺激活的肌肉一样发生，但在最大激活状态下的活性横桥数量比Ca²⁺激活的肌肉少。
