| Assay Method Information | |
| | Inhibition Assay |
| Description: | Cells were split 2-3 times weekly between 1:3 and 1:4. For binding assays and membrane preparations the cell culture medium was removed, cells were washed with PBS. Crude membranes for radioligand binding experiments were prepared by scraping the cells off the dishes in ice cold 20 mM HEPES/0.1 mM KCl/pH 7.2. The cell suspension was homogenized on ice (Ultra turrax, 3×20 sec.) and the homogenate was spun for 10 min (1° C., 1000 g, OPTIMA, SW28, 2800 U/min). The supernatant was than centrifuged for 40 min at 100000 g (1° C., OPTIMA, SW28, 23000 U/min). The membrane pellet was resuspended in 20 mM HEPES/0.1 mM KCl/pH 7.2, frozen and stored at −80° C.After thawing on the day of the assay, the membrane suspension was diluted further with 20 mM HEPES/0.1 mM KCl/pH 7.2.The incubation mixture of 200 μl contained 1.5 nmol/l 3H-Dofetilide, optimized amount of membrane preparation, 20 mM HEPES/0.1 mM KCl/(pH 7.2) and inhibitor in 1% DMSO. Nonspecific binding was estimated in the presence of 10 M Dofetilide. The samples were incubated for 90 min. at RT.Binding was terminated by filtration of the incubated membrane preparations using Filtermat B (Pharmacia, Uppsala Sweden) and a Micro Cell Harvester (Skatron, Lier, Norway). The Filtermat B had been presoaked with 1% polyethylenimine and carefully washed with 0.05 M Tris/HCl-buffer pH=7.7 after the filtration to separate free and bound radioactivity. The filters were counted in a scintillation counter (Betaplate 1205, Berthold, Wildbad, Germany) in order to determine the specific binding of [3H]-Dofetilide. |
| Affinity data for this assay | |
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