Figure 22. The effects of isoproterenol on integral Na⁺ fluxes.

Simulated major integral Na⁺ fluxes during one cardiac cycle in the isolated ventricular cell model are shown for control conditions (Panels A and C) and after application of 1 µM isoproterenol (Panels B and D). Pacing frequencies are 1 Hz (Panels A and B) and 5 Hz (Panels C and D). Major integral Na⁺ fluxes are shown after 300 s of stimulation. In Panels B and D 1 µM isoproterenol is applied at time t = 0 s. Here, J_Nav is the Na⁺ entering the caveolae compartment through the fast Na⁺ channels; J_Nab is the background Na⁺ influx; J_NaCa is the Na⁺ influx to the cytosol through the Na⁺/Ca²⁺ exchanger; and J_NaK is the Na⁺ outflux through the Na⁺-K⁺ pump.