Ravagli E, Bucchi A, Bartolucci C, Paina M, Baruscotti M, DiFrancesco D, Severi S
Computational Physiopathology Unit, Laboratory of Cellular and Molecular Engineering, D.E.I., University of Bologna, Via Venezia 52, 47521 Cesena, Italy.
The PaceLab, Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milano, Italy.
Prog Biophys Mol Biol. 2016 Jan;120(1-3):50-66. doi: 10.1016/j.pbiomolbio.2015.12.004. Epub 2015 Dec 21.
We used the Dynamic Clamp technique for i) comparative validation of conflicting computational models of the hyperpolarization-activated funny current, If, and ii) quantification of the role of If in mediating autonomic modulation of heart rate. Experimental protocols based on the injection of a real-time recalculated synthetic If current in sinoatrial rabbit cells were developed. Preliminary results of experiments mimicking the autonomic modulation of If demonstrated the need for a customization procedure to compensate for cellular heterogeneity. For this reason, we used a cell-specific approach, scaling the maximal conductance of the injected current based on the cell's spontaneous firing rate. The pacemaking rate, which was significantly reduced after application of Ivabradine, was restored by the injection of synthetic current based on the Severi-DiFrancesco formulation, while the injection of synthetic current based on the Maltsev-Lakatta formulation did not produce any significant variation. A positive virtual shift of the If activation curve, mimicking the Isoprenaline effects, led to a significant increase in pacemaking rate (+17.3 ± 6.7%, p < 0.01), although of lower magnitude than that induced by real Isoprenaline (+45.0 ± 26.1%). Similarly, a negative virtual shift of the activation curve significantly lowered the pacemaking rate (-11.8 ± 1.9%, p < 0.001), as did the application of real Acetylcholine (-20.5 ± 5.1%). The Dynamic Clamp approach, applied to the If study in cardiomyocytes for the first time and rate-adapted to manage intercellular variability, indicated that: i) the quantitative description of the If current in the Severi-DiFrancesco model accurately reproduces the effects of the real current on rabbit sinoatrial cell pacemaking rate and ii) a significant portion (50-60%) of the physiological autonomic rate modulation is due to the shift of the If activation curve.
i）对超极化激活的起搏电流（If）相互矛盾的计算模型进行比较验证，以及ii）量化If在介导心率自主调节中的作用。我们开发了基于向兔窦房结细胞注射实时重新计算的合成If电流的实验方案。模拟If自主调节的实验初步结果表明，需要一种定制程序来补偿细胞异质性。因此，我们采用了细胞特异性方法，根据细胞的自发放电频率来缩放注入电流的最大电导率。应用伊伐布雷定后显著降低的起搏频率，通过基于Severi-DiFrancesco公式注入合成电流得以恢复，而基于Maltsev-Lakatta公式注入合成电流则未产生任何显著变化。模拟异丙肾上腺素效应的If激活曲线正向虚拟移位导致起搏频率显著增加（+17.3 ± 6.7%，p < 0.01），尽管幅度低于真实异丙肾上腺素引起的增加（+45.0 ± 26.1%）。同样，激活曲线的负向虚拟移位显著降低了起搏频率（-11.8 ± 1.9%，p < 0.001），真实乙酰胆碱的应用也有相同效果（-20.5 ± 5.1%）。动态钳方法首次应用于心肌细胞的If研究，并进行了速率适配以处理细胞间变异性，结果表明：i）Severi-DiFrancesco模型中If电流的定量描述准确再现了真实电流对兔窦房结细胞起搏频率的影响，以及ii）生理性自主速率调节的很大一部分（50 - 60%）归因于If激活曲线的移位。
