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Assay Method Information

Assay Name:  Binding Assay
Description:  To prepare cell membranes with human α1- and α2-adrenergic receptors, CHO cells stably overexpressing α1- and α2-adrenergic receptors are lysed and then subjected to differential centrifugation. After lysis in binding buffer (50 mM tris(hydroxymethyl)aminomethane/1 N hydrochloric acid, 5 mM magnesium chloride, pH 7.4) using an Ultra Turrax (Jahnke & Kunkel, Werk), the homogenate is centrifuged at 1000 g and at 4 C. for 10 min. The resulting sediment is discarded and the supernatant is centrifuged at 20 000 g and at 4 C. for 30 min. The supernatant is discarded and the sediment is resuspended in binding buffer and stored at −70 C. until the binding test. For the binding test the radioligands 3H-MK-912 (2.2-3.2 TBq/mmol, PerkinElmer) (0.4 nM for α2C-adrRez and 1 nM for α2A-adrRez), 0.25 nM 3H-prazosin (α1AC-adrRez; 2.6-3.3 TBq/mmol, PerkinElmer), 0.25 nM 3H-rauwolscine (α2B-adrRez, 2.6-3.2 TBq/mmol, PerkinElmer) are incubated for 60 minutes with 5-20 μg cell membranes in binding buffer (total test volume 0.2 ml) in the presence of the test substances at 30 C. in 96-well filter plates (FC/B glass fibre, Multiscreen Millipore). The incubating is terminated by aspiration of the unbound radioactivity and the plates are then washed with binding buffer and subsequently dried at 40 C. for 1 hour. Liquid scintillator (Ultima Gold, PerkinElmer) is then added and the radioactivity that remained on the plates is measured in a liquid scintillation counter (Microbeta, Wallac). Non-specific binding is defined as radioactivity in the presence of 1-10 μM WB-4101 (α2C-adrRez and α2A-adrRez), prazosin (α2B-adrRez and α1AC-adrRez) (all from Sigma) and is generally <25% of the bound total radioactivity.
Affinity data for this assay
 

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Last update November 1, 2007
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