Assay Method Information

Assay Name:  URAT1-Model Assay
Description:  HEK293 human embryonic kidney cells (ATCC# CRL-1573) were propagated in EMEM tissue culture medium as described by ATCC in an atmosphere of 5% CO2 and 95% air. Transfections of HEK293 cells with a model URAT1 construct was performed using L2000 transfection reagent (Invitrogen) as described by the manufacturer. After 24 h the transfected cells were split into 10 cm tissue culture plates and grown for 1 day after which the medium was replaced with fresh growth medium containing G418 (Gibco) at 0.5 mg/ml final concentration. Drug-resistant colonies were selected after approximately 8 days and then tested for 14C-uric acid transport activity. The HEK293/URAT1-model cells are plated on Poly-D-Lysine Coated 96-well Plates at a density of 125,000 cells per well.Cells were grown overnight (20-26 hours) at 37° C. in an incubator. Plates were allowed to come to room temperature and media was washed out with one wash of 250 μl of Wash Buffer (125 mM Na Gluconate, 10 mM Hepes ph 7.3). Compound or vehicle is added in assay buffer with 14C-uric acid for a final concentration of 12504 Uric Acid with a specific activity of 54 mCi/mmol. Assay Buffer is 125 mM Sodium Gluconate, 4.8 mM Potassium Gluconate, 1.2 mM Potassium phosphate, monobasic, 1.2 mM magnesium sulfate, 1.3 mM Ca Gluconate, 5.6 mM Glucose, 25 mM HEPES, pH 7.3. Plates were incubated at room temperature for 10 minutes then washed 3 times with 50 μl Wash Buffer and 3 times with 250 μl Wash Buffer. Microscint 20 Scintillation Fluid was added and plates were incubated overnight at room temperature to equilibrate. Plates are then read on the TopCount Plate Reader and an EC50 value generated. (See Enomoto et al, Nature, 2002, 417, 447-451 and Anzai et al, J. Biol. Chem., 2004, 279, 45942-45950.)
Affinity data for this assay
 

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