Sildenafil citrate does not affect cardiac contractility in human or dog heart

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Abstract
SUMMARYObjective: This study evaluated whether sildenafil citrate, an oral treatment for erectile dysfunction and a selective inhibitor of phosphodiesterase type 5 (PDE5) with modest vasodilating properties, affects cardiac contractility in vitro.Research design and methods: Slices of freshly obtained human (n = 2) or dog (n = 3) atrial appendage were suspended in organ baths containing Krebs—Ringer bicarbonate buffer (pH 7.4, 37°C) bubbled continuously with 95% O2 and 5% CO2, and isometric tension was recorded using a Gould physiograph. Contractions were elicited by 1-Hz electric pacing. After 15min of equilibration, 1\M sildenafil was added to the bath, followed 15min later (human and dog) by 5|iM epinephrine, an inotropic agent, and 10min later (dog) by 88|iM 3-isobutyl-1 -methylxanthine(IBMX), a nonselective PDE inhibitor. In a separate experiment, cyclic guanosine monophosphate levels and PDE, protein kinase G, and protein kinase A activities were determined.Results: Addition of 1 |iM sildenafil to i...