FIGURE 3.

AP prolongation in SERCA2-KO myocytes relies upon augmented L-type calcium current. (A) Superfusing FF (n = 7) and KO (n = 8) myocytes with nominally Ca²⁺ free extracellular solution abolishes early AP prolongation in KO myocytes, while elevating extracellular Ca²⁺ to 1.8 mM exaggerates the difference in APD₅₀ and APD₇₀ (**p < 0.05 FF vs. KO at 1.8 mM Ca²⁺; and p < 0.05 KO at 1.8 mM vs. 0 mM Ca²⁺, *p < 0.0 KO at 1.8 mM vs. 0 mM Ca²⁺). (B) I_CaL blockade via Nifedipine (1 μM) achieves similar normalization of APD₅₀ and APD₇₀ in KO myocytes (n = 7) relative to FF (n = 7). **p < 0.05 FF vs. KO in control superfusate; and p < 0.05 KO in control vs. Nifedipine. All panels: data are means ± SEM.