Figure 6. Mathematical simulation of Na⁺–Ca²⁺ exchange current as a function of membrane potential at selected [Na⁺]_i and [K⁺]_o.

Na⁺–Ca²⁺ exchange current is shown assuming control (10 mm) and elevated [Na⁺]_i. Arrows denote our experimental measurements of diastolic membrane potentials resulting from superfusion of ventricular myocytes with a solution containing selected [K⁺]_o (mm). This simulation was done using the software described in Puglisi & Bers (2001).