FIGURE 1.

Kinetics of I_Ca,L. (Top) Voltage dependence of steady-state probabilities (d_L∞, f_L∞) and time constants for I_Ca,L activation (τ_dL) and inactivation (τ_fL). Equations used for the current (modified) model are shown with the thick lines (labeled “PM”). For comparison, those for existing (original) models are also shown with the thin lines: PB, Priebe and Beuckelmann (15); TNNP, ten Tusscher et al. (16); CRN, Courtemanche et al. (19). The experimental data for d_L∞, f_L∞, and τ_fL are from Bénitah et al. (21) (circles), Pelzmann et al. (22) (squares), and Li et al. (23) (hexagons). (Bottom) Computed voltage-clamp records for I_Ca,L (left) and peak I_Ca,L-V relationship (right). Currents were evoked by 300-ms step pulses from a holding potential of −50 mV to test potentials ranging from −30 to +50 mV in 10 mV increments. Simulating the whole-cell perforated-patch recording, [Ca²⁺]_i was not clamped, whereas [Na⁺]_i and [K⁺]_i were fixed at 5 and 140 mM, respectively. The experimental data for the peak I_Ca,L-V relation are from Bénitah et al. (21) (open circles), Pelzmann et al. (22) (squares), and Li et al. (23) (hexagons).