Fig. 12.

Insights gleaned using numerical model simulations on Na⁺ regulation of the cell membrane ion currents (via direct and indirect effects). Plots of continuous membrane current changes (left) for over the entire range of [Na⁺]_i from 8 to 14 mmol/l illustrated with their representative waveforms (right) at the 4 key [Na⁺]_i. Colors representing different [Na⁺]_i match colors in Fig. 9. The overlapped traces are synchronized at the AP overshoot (vertical dashed lines). A: L-type Ca²⁺ current (I_CaL). B: T-type Ca²⁺ current (I_CaT). C: rapid delayed rectifier K⁺ current (I_Kr). D: funny current (I_f). E: Na⁺ background current (I_bNa). F: Na⁺/K⁺ ATPase current (I_NaK, remaining after I_NaK inhibition by DG).