PDE4 controls the β-adrenergic stimulation of the cardiac excitation-contraction coupling in right ventricular cardiomyocytes isolated from healthy and heart failure pigs

PDE3 is considered as the main isoform controlling cardiac function in large mammals. Recently, we showed that PDE4 controls cAMP levels upon β-adrenergic (βAR) regulation in human atrial [1] and canine ventricular cells [2] . However, it was reported that it does not influence contractility of human failing myoardium [3] . Thus, a role for PDE4 to control cardiac excitation-contraction coupling (ECC) in larger mammals is controversial. Here, we investigated the role of PDE4 to control cAMP levels and ECC in a porcine model of repaired tetralogy of Fallot (rToF), which leads to heart failure. PDE4A, 4B and 4D isoforms were detected in the heart, with decreased expression in rToF. Isolated right ventricular myocytes (RVMs) from control (Ctrl) and rToF pigs were loaded with 1 μM Fura-2 and paced at 1 Hz to record simultaneously Ca 2+ transients and sarcomere shortening, or infected with an adenovirus encoding the cAMP FRET sensor epac H187 to evaluate intracellular cAMP levels. In Ctrl RVMs, inhibition of PDE3 with cilostamide (Cil, 1 μM) or PDE4 with Ro-201724 (Ro, 10 μM) modestly affected basal cAMP levels while concomitant inhibition of both enzymes had a strong influence (+130 ± 14%, n  = 12, P 2+ transient amplitude and sarcomere shortening. Similar effects were found in RVMs from rTOF pigs. In Ctrl RVMs, Ro potentiated cAMP levels produced upon application of the βAR agonist isoprenaline (Iso, 10 nM) (+184 ± 15%, n  = 21, P n  = 18, P 2+ waves ( P