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HERG Effects on Ventricular Action Potential Duration and Tissue Vulnerability: A Computational Study

机译:HERG对心室动作电位持续时间和组织易损性的影响:一项计算研究

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The mutations to hERG (the human Ether-a-go-go Related Gene) that cause long QT syndromes produce effects on the rapid delayed rectifier K~+ current I_(Kr) and, therefore, action potential duration (APD). These mutations can affect various properties that determine I_(Kr) kinetics. We used computational models of human ventricular my-ocytes to identify which of these properties, when altered, cause profound changes to APD and transmural dispersion of repolarisation (TDR). Such increases in both APD and TDR is caused by a positive shift of activation V_(0.5), a negative shift of inactivation V_(0.5), or by reducing maximal conductance. The largest reduction in APD is achieved by a positive shift of inactivation V_(0.5)- Altering the time constant of activation had relatively little effect. When two or more parameters were altered simultaneously, shifting inactivation V_(0.5) had the dominant effect on APD, except for some extreme shifts of activation V_(0.5) or moderate reductions of maximal conductance. HERG mutations observed clinically lie in the parameter range where maximal conductance has the dominant effect. Bifurcation analysis showed stable steady states (corresponding to physiological resting membrane potential) at all parameter values, and no APD alternans. We conclude that increased APD due to hERG mutations seen clinically are a combined effect of alterations to I_(Kr) kinetic parameters that, in isolation, cause either shortening or prolongation of the AP. Therapeutics that alter I_(Kr) conductance are potentially most beneficial.
机译:导致长时间QT综合征的hERG(人类以太相关基因)突变对快速延迟整流K〜+电流I_(Kr)产生影响,因此对动作电位持续时间(APD)产生影响。这些突变会影响决定I_(Kr)动力学的各种特性。我们使用人类心室肌细胞的计算模型来确定这些属性中的哪些,当改变时,会引起APD的深刻变化和透极化的复极化(TDR)。 APD和TDR的这种增加是由激活V_(0.5)的正向移动,失活V_(0.5)的负向移动或减小最大电导引起的。 APD的最大降低是通过失活V_(0.5)的正向位移实现的。更改激活时间常数的影响相对较小。当同时更改两个或多个参数时,除激活V_(0.5)的一些极端变化或最大电导的适度降低外,移动失活V_(0.5)对APD具有主导作用。临床上观察到的HERG突变位于最大电导起主要作用的参数范围内。分叉分析显示在所有参数值下都稳定的稳态(对应于生理静息膜电位),并且没有APD交替蛋白。我们得出的结论是,由于临床上见到的hERG突变而导致的APD升高是I_(Kr)动力学参数改变的综合作用,这些改变单独地导致AP缩短或延长。改变I_(Kr)电导的疗法可能是最有益的。

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