Abstract

Birds acquired endothermy and a four-chambered heart independently from mammals in the course of evolution. Though avian embryos are widely used in experiments, little is known about the adult avian heart. Recent studies have shown that, despite a large evolutionary distance, the set of repolarizing potassium currents in avian myocardium resembles that in mammalian heart as well as that in humans. This allows for proposing birds as a potential model in experimental cardiology. The present study for the first time describes inward rectifier currents in working myocardium of quail. Using patch clamp method, we recorded main background inward rectifier current I_K1 was recorded in isolated atrial and ventricular cardiomyocytes of quail. Both inward and outward components of I_K1 in ventricular cells were larger than those in atrial cells, while there were no differences in voltage dependence of inward rectification. Acetylcholine and carbachol induced activation of acetylcholine-dependent inward rectifier current I_KACh in atrial but not in ventricular myocytes. I_KACh in atrial myocytes was sensitive to tertiapin. Constitutively active I_KACh has not been detected. In multicellular preparations of the quail right atrium, carbachol induced hyperpolarization and shortening of action potentials, while no such effects were observed in preparations of the right ventricle. Activation of I_KACh upon application of carbachol was dose-dependent with EC₅₀ = 4.922 × 10^–7 М. The described distribution of inward rectifier currents in avian myocardium is similar to that in mammalian species, which are widely used as model objects in experimental cardiology.

中文翻译：

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日本鹌鹑（Coturnix japonica）工作心肌中的内向整流电流 IK1 和 IKACh

摘要

鸟类在进化过程中独立于哺乳动物获得了恒温和四腔心脏。尽管鸟类胚胎被广泛用于实验，但对成年鸟类心脏知之甚少。最近的研究表明，尽管进化距离很大，但鸟类心肌中的复极化钾电流与哺乳动物和人类心脏中的相似。这允许提出鸟类作为实验心脏病学的潜在模型。本研究首次描述了鹌鹑工作心肌中的内向整流电流。使用膜片钳方法，我们记录了鹌鹑的分离的心房和心室心肌细胞中的主要背景内向整流电流I _K1。I 的内部和外部组件心室细胞中的_K1大于心房细胞中的_K1，而内向整流的电压依赖性没有差异。乙酰胆碱和卡巴胆碱在心房而非心室肌细胞中诱导乙酰胆碱依赖性内向整流电流I _{KACh 的}激活。我_卡奇在心房肌细胞是tertiapin敏感。尚未检测到组成型活性I _KACh。在鹌鹑右心房的多细胞制剂中，氨甲酰胆碱诱导超极化和动作电位缩短，而在右心室的制剂中没有观察到这种影响。应用卡巴胆碱后I _{KACh 的}激活与 EC 呈剂量依赖性₅₀ = 4.922 × 10 ^–7 М。所描述的禽类心肌中内向整流器电流的分布类似于哺乳动物物种中的分布，后者被广泛用作实验心脏病学中的模型对象。