Assay Method Information
Assay Name:  Binding Assay to Sigma Receptors
Description:  The σ binding assays were performed according to Ganapathy et al. (Ganapathy, M. E.; Prasad, P. D.; Huang, W.; Seth, P.; Leibach, F. H.; Ganapathy, V. Molecular and ligand-binding characterization of the sigma-receptor in the Jurkat human T lymphocyte cell line. J. Pharmacol. Exp. Ther. 1999, 289, 251-260). The σ1 binding assay was carried out by incubating Jurkat cell membranes (10-20 mg protein per tube) with [3H](+)-pentazocine (15 nM) and a range of concentrations of tested compounds, at 37° C. for 2 hours, in 5 mM Tris/HCl buffer (pH=7.4). The σ2 binding assay was performed by incubating Jurkat cell membranes (10-20 mg protein per tube) with [3H]-DTG (25 nM) in presence of (+)-pentazocine (1 μM) to saturate σ1 receptors, and a range of concentrations of tested compounds, at room temperature for 1 hour in 5 mM Tris/HCl buffer (pH=7.4). The final assay volume was 0.5 mL. Binding was terminated by rapid filtration through Wathman GF/B filters, which were then washed with 5×1 mL ice-cold NaCl solution and allowed to dry before bound radioactivity was measured using liquid scintillation counting. Nonspecific binding was determined, in both assays, under similar conditions, but in presence of 10 μM unlabeled haloperidol. Inhibition constants (Ki) were calculated from the IC50 values according to the method of Cheng and Prusoff (Cheng, Y.; Prusoff, W. H. Relationship between the inhibition constant (Ki) and the concentration of inhibitor which causes 50 percent inhibition (IC50) of an enzymatic reaction. Biochem Pharmacol. 1973, 22 (23), 3099-108):K i = IC 50 1 + L K dWhere IC50=Inhibitory concentration at 50% L=Concentration of radioligand Kd=Affinity constant of radioligandThe σ1 binding assay was carried out with [3H](+)-pentazocine (L=15 nM, Kd=16 nM) as radioligand and the a binding assay with [3H]-DTG (L=25 nM, Kd=80.84 nM).
Affinity data for this assay
 
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