Isoprenaline: A Potential Contributor in Sick Sinus Syndrome—Insights from a Mathematical Model of the Rabbit Sinoatrial Node

Table 3

Model parameter values.

Glossary		Central SAN model	Peripheral SAN model
𝐶𝑚	Cell membrane capacitance	20 pF	65 pF
𝑔Na	Maximum 𝑖Na conductance	0 μS/pF	1.85×10^−8𝜇S/pF
𝑔K,Ach,max	Maximum 𝑖K,Ach conductance	3.53×10^−10 μS/pF	1.218×10^−9𝜇S/pF
𝑔Ca,𝐿	Maximum 𝑖Ca,𝐿 conductance	2.9×10^−4 μS/pF	1.0×10^−3𝜇S/pF
𝑔𝑓,Na	Maximum 𝑖𝑓,Na conductance	0.27×10^−4 μS/pF	1.05×10^−4𝜇S/pF
𝑔𝑓,K	Maximum 𝑖𝑓,K conductance	0.27×10^−4 μS/pF	1.05×10^−4𝜇S/pF
𝑔K,𝑟	Maximum 𝑖K,𝑟 conductance	3.99×10^−5 μS/pF	2.46×10^−4𝜇S/pF
𝑔𝐾,𝑠	Maximum 𝑖𝐾,𝑠 conductance	2.59×10^−5 μS/pF	1.6×10^−4𝜇S/pF
𝑔st	Maximum 𝑖st conductance	0.75×10^−5 μS/pF	0 μS/pF
𝐸Ca,𝐿	Apparent reversal potential for 𝑖Ca,𝐿	46.4 mV	46.4 mV
𝐸st	Apparent reversal potential for 𝑖st	37.4 mV	37.4 mV
Na^+𝑜	Extracellular Na^+ concentration	140 mM	140 mM
K^+𝑜	Extracellular K^+ concentration	5.4 mM	5.4 mM
𝐾0.5,K,Ach	[Ach] that produces a half-maximal activation of 𝑔K,Ach,max	0.28 μM	0.28 μM
𝐾0.5,Ca	[Ach] that produces a half-maximal block of 𝑖Ca,𝐿	0.09 μM	0.09 μM
𝐾0.5,Ca′	[Iso] that produces a half-maximal increase of 𝑖Ca,𝐿	7 nM	7 nM
𝐾0.5,𝑓	[Ach] that produces a half-maximal shift of 𝑖𝑓 activation curve	1.26×10^−2 μM	1.26×10^−2 μM
𝐾0.5,𝑓′	[Iso] that produces a half-maximal shift of 𝑖𝑓 activation curve	13.5 nM	13.5 nM
𝐾0.5,𝑔K	[Iso] that produces a half-maximal increase of 𝑔K,𝑟	19 nM	19 nM
𝐾0.5,Kacti	[Iso] that produces a half-maximal shift of 𝑖K,𝑟 activation curve	7.5 nM	7.5 nM
𝐾0.5,𝜏K,𝑟	[Iso] that produces a half-maximal decrease of 𝜏K,𝑟	24 nM	24 nM
𝐾0.5,st	[Iso] that produces a half-maximal Increase of 𝑖st	33 nM	33 nM
𝑃up	Rate constant of Ca^2+ uptake by 𝑗up of the network SR	0.01 mM/ms	0.02 mM/ms
𝑛K,Ach	𝑖K,Ach affected by [Ach] and Hill coefficient	1.5	1.5
𝑛𝑓	𝑖𝑓 affected by [Ach] and Hill coefficient	0.69	0.69
𝑛up	SR Ca^2+ uptake and Hill coefficient	2	2
𝑛𝑓′	𝑖𝑓 affected by [Iso] and Hill coefficient	0.392	0.392
𝑆Na	Percentage change of 𝑖Na conductance induced by DelF1617 mutation	0.38	0.38
𝑆𝜏ℎ1	Percentage change of the fast-inactivation time constants of 𝑖Na induced by DelF1617 mutation	2.18	2.18
𝑆𝜏ℎ2	Percentage change of the slow-inactivation time constants of 𝑖Na induced by DelF1617 mutation	2.75	2.75
𝑆ℎ	Parameter of the shift in the inactivation curve of 𝑖Na induced by DelF1617 mutation	0.128	0.128
𝑏max	Maximum fraction of 𝑖Ca,𝐿 block caused by Ach	0.56	0.56
𝑠max	Maximum shift of 𝑖𝑓 activation curve caused by Ach	−7.2 mV	−7.2 mV
𝑓Ca,max	Maximum percentage increase of 𝑖Ca,𝐿 caused by Iso	0.54	0.54
𝑓𝐾,max	Maximum percentage increase of 𝑖K,𝑟 caused by Iso	1.87	1.87
𝑓st.max	Maximum percentage increase of 𝑖st caused by Iso	1.0	1.0
𝑆𝑓,max	Maximum activation curve shift of 𝑖𝑓 caused by Iso	9.62 mV	9.62 mV
𝑆K,max	Maximum activation curve shift of 𝑖K,𝑟 caused by Iso	−15 mV	−15 mV
𝑑𝜏K,𝑟,max	Maximum decrease of 𝜏K,𝑟, caused by Iso	3.0	3.0
𝛼Iso	Percentage increase of the SR Ca^2+ release fluxes caused by Iso	0.2	0.2
𝛽Iso	Percentage decrease of the SR Ca^2+ uptake caused by Iso	0.2	0.2