Figure 2. Relative contribution of small-conductance Ca2+-activated K+ (SK)-current and other K+-currents to action potential (AP) duration and resting membrane potential (RMP) in the in silico human atrial cardiomyocyte model and protein levels of SK channel subunits in right-atrial (RA)-cardiomyocytes from Ctl- and cAF-patients.

A, Steady-state APs during 1-Hz pacing in the populations of Ctl (left) and cAF (right) models. B, Relative contribution of the maximal conductance of the transient-outward K⁺-current (Gto); rapid, slow or ultra-rapid delayed-rectifier K⁺-currents (GKr, GKs and GKur, respectively); basal inward-rectifier K⁺-current (composed of GK1, empty bars; and constitutively-active acetylcholine-activated inward-rectifier K⁺ current GK,ACh,c, hatched bars, 10% in Ctl and 20% in cAF); and SK-current (GSK), as well as affinity of SK-current for intracellular Ca²⁺ (Kd,SK) to AP duration at 50%- or 90%-repolarization (APD₅₀; APD₉₀) or RMP in Ctl (white bars) or cAF (red bars) model populations. Each bar represents a regression coefficient linking a certain model parameter to a certain AP feature. The coefficient can be used to predict the value of each AP feature after applying a known perturbation in the baseline value of the model parameter, as detailed in the online-only Data Supplement. C, Representative Western blots (left) and quantification of SK1, SK2 and SK3 proteins in RA-cardiomyocytes from Ctl- and cAF-patients. N-numbers indicate number of patients. P-values are based on Mann-Whitney tests comparing Ctl vs. cAF.