Assay Method Information

Assay Name:  Radioligand Binding Assay
Description:  HEK-293 cells stably expressing the human or feline FP receptor, or EP1, EP2, or EP4 receptors were washed with TME buffer, scraped from the bottom of the flasks, and homogenized for 30 sec using a Brinkman PT 10/35 polytron. TME buffer was added to achieve a final 40 ml volume in the centrifuge tubes (the composition of TME is 100 mM TRIS base, 20 mM MgCl2, 2M EDTA; 10N HCl is added to achieve a pH of 7.4).The cell homogenate was centrifuged at 19000 r.p.m. for 20 min at 4° C. using a Beckman Ti-60 rotor. The resultant pellet was resuspended in TME buffer to give a final 1 mg/ml protein concentration, as determined by Biorad assay. Radioligand binding competition assays vs. [3H-]17-phenyl PGF2a (5 nM) were performed in a 100 μl volume for 60 min. Binding reactions were started by adding plasma membrane fraction. The reaction was terminated by the addition of 4 ml ice-cold TRIS-HCl buffer and rapid filtration through glass fiber GF/B filters using a Brandel cell harvester. The filters were washed 3 times with ice-cold buffer and oven dried for one hour.[3H] PGE2 (specific activity 180 Ci mmol) was used as the radioligand for EP receptors. [3H] 17-phenyl PGF2a was employed for FP receptor binding studies. Binding studies employing EP1, EP2, EP4 and FP receptors were performed in duplicate in at least three separate experiments. A 200 μl assay volume was used. Incubations were for 60 min at 25° C. and were terminated by the addition of 4 ml of ice-cold 50 mM TRIS-HCl, followed by rapid filtration through Whatman GF/B filters and three additional 4 ml washes in a cell harvester (Brandel).
Affinity data for this assay
 

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