Hemodynamic, Hormonal, and Renal Actions of Phosphodiesterase-9 Inhibition in Experimental Heart Failure.

BACKGROUND:Phosphodiesterase-9 (PDE9) reduces natriuretic peptide (NP) signaling and may be involved in the pathophysiology of heart failure (HF). OBJECTIVES:This study investigated for the first time the integrated hemodynamic, endocrine, and renal effects of phosphodiesterase-9 inhibition (PDE9-I). METHODS:A total of 8 normal sheep and 8 sheep with pacing-induced HF received incremental intravenous boluses of PDE9-I (30, 100, and 300 mg PF-04749982 at 1-h intervals). RESULTS:PDE9-I dose-dependently increased plasma cyclic guanosine monophosphate (cGMP) in normal sheep (p < 0.05) while concurrently reducing circulating atrial natriuretic peptide levels (p < 0.01). Similar trends were evident in HF, resulting in significant elevations in the cGMP/NP ratio in both states (p < 0.001 and p < 0.05, respectively). PDE9-I also produced progressive falls in arterial pressure (HF: p < 0.001), atrial pressure (Normal: p < 0.001; HF: p < 0.001), and peripheral resistance (HF: p < 0.001), and transiently increased cardiac output at the top dose (Normal: p < 0.05; HF: p < 0.001). Inhibition of PDE9 had a negligible effect on circulating hormones at the lower doses, but post-high dose, acutely increased renin activity (Normal: p < 0.001; HF: p < 0.05), vasopressin (Normal: p < 0.001; HF: p < 0.01), and cyclic adenosine monophosphate (HF: p < 0.001). Plasma aldosterone increased briefly after high-dose PDE9-I in normal sheep, and fell following the top dose in HF. PDE9-I dose-dependently increased urinary cGMP in both states (both p < 0.001). In HF, this was associated with increases in urine volume (p < 0.01), sodium excretion (p < 0.01), and creatinine clearance (p < 0.001). CONCLUSIONS:PDE9-I improves NP efficacy in conjunction with beneficial hemodynamic and renal effects in experimental HF. These results support a role for PDE9 in HF pathophysiology and suggest its inhibition may constitute a novel therapeutic approach to this disease.