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Assay Method Information

Assay Name:  Functional Assay
Description:  The assay was performed as described below, using HEK293 cells transfected with rat TRPV1 (rTRPV1/HEK293). These cells had a geneticin selection marker and were grown in Dulbecco's Modified Eagle Medium (DMEM, Gibco BRL) supplemented with 10% fetal bovine serum, penicillin/streptomycin (50 units/mL), and 500 μg/mL geneticin in 5% CO2 at 37° C. Cells were passaged frequently, every 3-5 days, to avoid overgrowth, depletion of essential medium components, or acidic medium exposure. Cells were passaged using a brief wash in 0.05% trypsin with 1 mM EDTA, followed by dissociation in divalent-free phosphate-buffered saline (Hyclone #SH30028.02). Dissociated cells were seeded onto poly-D-lysine coated black-walled 96-well plates (Biocoat; Becton Dickinson #354640) at about 40,000 cells per well and grown for approximately 1 day in culture medium to near confluency. The assay buffer was composed of 130 mM NaCl, 2 mM KCl, 2 mM MgCl2, 10 mM HEPES, 5 mM glucose, and either 2 mM or 20 μM CaCl2. On the day of the experiment, the culture medium was replaced with 2 mM calcium assay buffer using an automated plate washer (ELx405; Biotek, VT). The cells were incubated in 100 μL/well Fluo-3/AM (2 μM; TEFLabs #0116) with Pluronic F127 (100 μg/mL; Sigma #P2443) for 1 h at rt in the dark. After loading the cells, the dye solution was replaced with 50 μL/well of 20 μM calcium assay buffer using the ELx405 plate washer. Test compounds (50 μL/well) were added to the plate and incubated for 30 min. Intracellular Ca2+ levels were subsequently assayed using a Fluorometric Imaging Plate Reader (FLIPR™ instrument, Molecular Devices, CA) to simultaneously monitor Fluo-3 fluorescence in all wells (λexcitation=488 nm, λemission=540 nm) during challenge with agonist (capsaicin). The IC50 values were determined. Cells were challenged with 150 nM capsaicin and the fluorescence counts were captured following agonist addition at a sampling rate of 0.33 Hz. The contents of the wells were mixed 3 times (40 μL mix volume) immediately after the additions were made. Concentration dependence of block was determined by exposing each well of cells in duplicate rows of a 96 well plate to a serial dilution of test compound. The concentration series usually started at 10 μM with a three-fold serial decrement in concentration. The magnitude of the capsaicin response was determined by measuring the change in fluo3 fluorescence before and 100 seconds after the addition of the agonist.
Affinity data for this assay
 

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Last update November 1, 2007
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