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首页> 外文期刊>The Journal of Experimental Biology >Contractile properties of atrial and ventricular myocardium of the heart of rainbow trout Oncorhynchus mykiss: effects of thermal acclimation
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Contractile properties of atrial and ventricular myocardium of the heart of rainbow trout Oncorhynchus mykiss: effects of thermal acclimation

机译：虹鳟鱼Oncorhynchus mykiss的心房和心室心肌的收缩特性：热适应的影响

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摘要

Atrial and ventricular myocardium perform different tasks in the pumping work of the vertebrate heart, which are reflected in their contractile properties. Although atrial contraction is assumed to have an important role in the function of fish heart, the contractile properties of atrial and ventricular myocardium have not been directly compared in any fish species. The objective of this study was to clarify any contractile differences in the heart of teleost fish and, in particular, to elucidate the contribution of myofibriilar ATPase and intracellular Ca~(2+) stores to the characteristics of atrial and ventricular contraction. Experiments were conducted on thermally acclimated rainbow trout Oncorhynchus mykiss to determine whether the effects of temperature adaptation are the same in atrial and ventricular tissue. It was shown that the rate of isometric contraction is much faster in atrial than in ventricular tissue of the fish heart and that acclimation to cold increases the rate of contraction in both cardiac compartments. The rapid contraction kinetics of the atrial tissue were associated with higher myofibriilar ATPase activity and faster Ca~(2+) uptake rate of the sarcoplasmic reticulum (SR) compared with ventricular tissue. Similarly, the faster kinetics of contraction following cold acclimation could be attributed to enhancement of the myofibrillar and/or SR function. The atrio-ventricular and temperature-induced differences were also expressed in therecovery of force from inactivation, i.e. in the mechanical restitution. The refractory period and the rate constant of force restitution were shorter in atrial than in ventricular muscle tissue. Similar differences also existed between the tissues of cold-acclimated (CA, 4 deg C) and warm-acclimated (WA, 17~C) fish. The fast recovery of force from inactivation in the heart of the CA trout was, at least in part, due to more active SR. Furthermore, it was shown that the force of atrial contraction in the CA trout is sensitive to ryanodine (10 #mu#mol i-I), a Ca~(2+)-release channel blocker of SR, at physiological body temperature (4 deg C) and at a physiological pacing rate (0.6 Hz). This findingindicates that the Ca~(2+) stores of SR contribute to activation of cardiac contraction in the fish heart, and that the SR of fish heart is able to retain its Ca~(2+) load at Iow body temperatures, i.e. the Ca~(2+) release channels of SR are not leaky in the cold. The present data show that in the atrial tissue of CA trout, the SR directly contributes to the cytosolic Ca~(2+) and that in the atrium and ventricle of CA trout, the SR significantly accelerates the recovery of contractility from inactivation. The fast recovery from inactivation allows relatively high heart rates and therefore adequate cardiac outputs at low environmental temperatures for the cold-active rainbow trout.
机译：心房和心室心肌在脊椎动物心脏的泵送工作中执行不同的任务，这反映在它们的收缩特性中。尽管心房收缩被认为在鱼心的功能中具有重要作用，但尚未在任何鱼类中直接比较心房和心室心肌的收缩特性。这项研究的目的是弄清硬骨鱼心脏中的任何收缩差异，尤其是阐明肌纤维ATPase和细胞内Ca〜（2+）储存对心房和心室收缩特征的贡献。对热适应的虹鳟Oncorhynchus mykiss进行了实验，以确定温度适应的作用在心房和心室组织中是否相同。结果表明，等距收缩的速率在心房中比在鱼心的心室组织中快得多，而适应寒冷会增加两个心室的收缩速率。与心室组织相比，心房组织的快速收缩动力学与肌纤维网状肌（SR）的更高的肌纤维ATPase活性和更快的Ca〜（2+）吸收速率有关。类似地，冷驯化后收缩的更快动力学可以归因于肌原纤维和/或SR功能的增强。房室和温度引起的差异也表现在失活力的恢复中，即机械恢复中。心房的不应期和恢复力的速率常数比心室肌组织要短。在冷适应（CA，4摄氏度）和热适应（WA，17摄氏度）鱼的组织之间也存在类似的差异。从CA鳟鱼心脏的失活中快速恢复力量至少部分是由于SR更活跃。此外，研究表明，在生理温度（4摄氏度）下，CA鳟鱼的心房收缩力对SR的Ca〜（2+）释放通道阻滞剂ryanodine（10＃mu＃mol iI）敏感。 ）并以生理起搏频率（0.6 Hz）。这一发现表明SR的Ca〜（2+）储藏有助于鱼心中心脏收缩的激活，鱼心的SR能够在低体温下保持其Ca〜（2+）负荷，即SR的Ca〜（2+）释放通道在寒冷中不泄漏。目前的数据表明，在CA鳟鱼的心房组织中，SR直接作用于胞质Ca〜（2+），在CA鳟鱼的心房和心室中，SR显着促进了灭活的收缩性恢复。从失活中快速恢复可允许相对较高的心率，因此在低温环境下对于活跃的虹鳟鱼具有足够的心输出量。

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