Impact of temperature on cross-bridge cycling kinetics in rat myocardium
Impact of temperature on cross-bridge cycling kinetics in rat myocardium
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DOI：
10.1113/jphysiol.2007.138693
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发表时间：
2007-10-15
影响因子：
5.5
通讯作者：
Stienen, G. J. A.
中科院分区：
文献类型：
--
作者：
de Tombe, Pieter P.;Stienen, G. J. A.
心脏组织中收缩特性对细胞内钙的依赖性是一个高度合作的过程。在这里，研究了大鼠透化心脏小梁的收缩和能量特性的温度和钙依赖性，以提供对潜在动力学过程的新见解。肌丝 Ca2+ 敏感性随着温度在 15 至 25°C 之间显着增加，而其陡度与温度无关。观察到主动张力与 ATP 水解的 Ca2+ 激活速率之间存在正比关系；这种关系的斜率（张力成本）高度依赖于温度。快速释放-再拉伸动作 (k(tr)) 之后的张力即发展速率以复杂的方式取决于收缩激活水平和温度。在饱和钙水平下，ktr 和 Ca2+ 激活的 ATP 水解速率的温度依赖性 (Q(10)) 相似（Q10 类似于 3.5），并且显着高于最大张力（T-max；Q(10) 类似于 1.3）或张力成本（Q(10) 类似于 2.5）的 Q10。相反，在低收缩激活水平（类似于 T-max 的 5%）下，k(tr) 的 Q(10) 与张力成本相似，并且显着低于该收缩激活水平下 Ca2+ 激活的 ATP 水解的 Q(10)。我们的结果与以下假设一致：在高水平的收缩激活下，张力重建速率和 Ca2+ 激活的 ATP 水解速率由表观跨桥附着和脱离率决定，而在低水平下，ktr 受到跨桥脱离率的限制。另一方面，张力成本仅由所有温度和收缩激活水平下的跨桥脱离动力学决定。
The dependence of contractile properties on intracellular calcium in cardiac tissue is a highly cooperative process. Here, the temperature and calcium dependence of contractile and energetical properties in permeabilized cardiac trabeculae from rat were studied to provide novel insights into the underlying kinetic processes. Myofilament Ca2+ sensitivity significantly increased with temperature between 15 and 25 degrees C, whereas its steepness was independent of temperature. A direct proportionality between active tension and Ca2+-activated rate of ATP hydrolysis was observed; the slope of this relationship (tension cost) was highly temperature dependent. The rate of tension i-edevelopment following a quick release-restretch manoeuvre (k(tr),) depended in a complex manner on the level of contractile activation and on temperature. At saturating calcium levels, the temperature dependence (Q(10)) of ktr and Ca2+-activated ATP hydrolysis rate were similar (Q10 similar to 3.5), and significantly higher than the Q10 for maximum tension (T-max; Q(10) similar to 1.3) or tension cost (Q(10) similar to 2.5). In contrast, at a low level of contractile activation (similar to 5% of T-max), the Q(10) of k(tr) was similar to that of tension cost, and significantly lower than the Q(10) of Ca2+-activated ATP hydrolysis at that level of contractile activation. Our results are consistent with the hypothesis that at high levels of contractile activation, the rates of tension redevelopment and Ca2+-activated ATP hydrolysis are determined by both apparent cross-bridge attachment and detachment rates, while at low levels, ktr is limited by cross-bridge detachment rate. Tension cost, on the other hand, is determined solely by cross-bridge detachment kinetics at all temperatures and levels of contractile activation.