CHEMBL5738397

PDE3A Enzyme Inhibition: The commercially available 3H-cAMP Scintillation Proximity Assay (SPA, Perkin Elmer) system was used for enzyme inhibition studies. For the determination of the in vitro effect of example compounds on the PDE3A reactions 2 μl of the respective example compound solution in DMSO (serial dilutions) were placed in wells of microtiter plates (Isoplate-96/200W; Perkin Elmer). 50 μl of a dilution of PDE3A cell extract from Sf9 cells overexpressing human full length PDE3A (SB Drug Discovery, UK) in buffer A (50 mM Tris/HCl pH 7.5, 8.3 mM MgCl2, 1.7 mM EDTA, 0.2% BSA) was added. The dilution of the PDE3A cell extract was chosen such that the reaction kinetics was linear and less than 70% of the substrate was consumed (typical dilution 1:5000). The reaction was started by addition of 50 μl (0.025 μCi) of 1:2000 in buffer A w/o BSA diluted substrate [8-3H]adenosine 3′, 5′-cyclic phosphate (1 μCi/μl; Perkin Elmer). After incubation at room temperature for 60 min, the reaction was stopped by addition of 25 μl of a suspension containing 18 mg/ml yttrium scintillation proximity beads (Perkin Elmer) in water. The microtiter plates were sealed and measured in a Microbeta scintillation counter (PerkinElmer Wallac). IC50 values were determined from sigmoidal curves by plotting percentage PDE3A activity vs log compound concentration.